Father is brought back by engineers (4)
I believe the answer is:
'father' is the definition.
(I know that father can be written as sire)
'is brought back by engineers' is the wordplay.
'brought back' says the letters should be written backwards.
'by' is a charade indicator (letters next to each other).
'engineers' becomes 're' (abbreviation for Royal Engineers).
'is' written backwards gives 'si'.
(Other definitions for sire that I've seen before include "Make children" , "Old form of address to king - rise to it" , "Bear" , "Ancestor" , "Generator" .)