Conflict in river crossing at the front (7)
I believe the answer is:
forward
'the front' is the definition.
(thesaurus)
'conflict in river crossing' is the wordplay.
'conflict' becomes 'war' (war is a kind of conflict).
'in' indicates putting letters inside.
'river crossing' becomes 'ford' (I've seen this before).
'war' put into 'ford' is 'FORWARD'.
'at' acts as a link.
(Other definitions for forward that I've seen before include "To the front" , "Promote" , "Ahead; impertinent" , "going on" , "Onward" .)