Soldier on vessel to surrender (4,2)
I believe the answer is:
give in
'surrender' is the definition.
(I've seen this before)
'soldier on vessel' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue).
'on' means one lot of letters go next to another.
'vessel' becomes 'vein' (vein is a kind of vessel**).
'gi'+'vein'='GIVE IN'
'to' acts as a link.
(Other definitions for give in that I've seen before include "Cease arguing; submit" , "Cease fighting" , "Capitulate" , "Yield, submit" , "'Yield (4,2)'" .)