Engineers with demand for salvage (7)
I believe the answer is:
reclaim
'salvage' is the definition.
(I've seen this before)
'engineers with demand' is the wordplay.
'engineers' becomes 're' (abbreviation for Royal Engineers).
'with' says to put letters next to each other.
'demand' becomes 'claim' (claiming is a kind of demanding).
're'+'claim'='RECLAIM'
'for' acts as a link.
(Other definitions for reclaim that I've seen before include "Make (land) available for use" , "recovery like this" , "Bring under cultivation" , "Get back (eg from the sea)" , "Recover (materials/land) for subsequent use" .)