Bring back forces in front of gallery (9)
I believe the answer is:
reinstate
'bring back' is the definition.
(I've seen this before)
'forces in front of gallery' is the wordplay.
'forces in front of' becomes 'reins' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'reins'+'tate'='REINSTATE'
Can you help me to learn more?
(Other definitions for reinstate that I've seen before include "Restore, put back" , "Put back in place" , "Restore to previous position" , "Re-establish" , "Put back in position" .)