Engineers give up and retreat (6)
I believe the answer is:
recede
'retreat' is the definition.
(I know that retreat can be written as recede)
'engineers give up' is the wordplay.
'engineers' becomes 're' (Royal Engineers).
'give up' becomes 'cede' (synonyms).
're'+'cede'='RECEDE'
'and' is the link.
(Other definitions for recede that I've seen before include "Decree (anag) - ebb" , "Withdraw" , "Go backwards" , "Go back, ebb" , "Move backward" .)