Barbarian stifles lake rescue (7)
I believe the answer is:
salvage
'rescue' is the definition.
(salvage is a kind of rescue)
'barbarian stifles lake' is the wordplay.
'barbarian' becomes 'savage' ('savage' can be a synonym of 'barbarian').
'stifles' indicates putting letters inside.
'lake' becomes 'l'.
'savage' placed around 'l' is 'SALVAGE'.
(Other definitions for salvage that I've seen before include "Manage to retain" , "Property that's rescued" , "Collect discarded material" , "Preserve" , "Recover (cargo from wreck)" .)