Support for bush rose?

I have a shrub rose ("Wandering Minstrel") that I planted last year as a bare root. It didn't do much then but this year is starting to put on a good spurt of growth. Most of this, however, seems to be concentrated on one long stem coming up from the base, which is already very flimsy-looking. There are a couple more stems starting to grow but none as vigorous as this main one.

Should I:
(a) Put a support in for this long stem and let it keep growing?
(b) Cut it back and encourage more growth from the base?

I've tried to take some pictures to show the problem, not sure how effective they are though!

 

I can't see the base of the long stem 2nd_bassoon. Looking at your third picture is it coming directly out of the ground or attached to what looks like dead wood in front of it?

 

It's coming off the main rootball @Sheal - the deadwood was a stem when I originally planted it but died off over the winter.

 

If it's coming from the roots and not from the grafted stem it's a sucker from the rootstock and won't grow true. Prune or pull it out from the root it's attached too. The deadwood can be pruned out too.

 

Perhaps to add to Sheal's comment. Sometimes it is wise to scratch away the soil and make really certain where this shoot is coming from. The usual practice for removal is to tear the offender away. Doing this will also remove a small area of backing, thus the viable genes also go. To simply cut off the offender, basically the same or similar situation remains, like with taking cuttings....the source remains for future come back. Just a tip.