Father brought back expert quickly (5)
I believe the answer is:
apace
'quickly' is the definition.
(I know that quickly can be written as apace)
'father brought back expert' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'brought back' says the letters should be written backwards.
'expert' becomes 'ace' (ace can informally mean very good).
'pa' backwards is 'ap'.
'ap'+'ace'='APACE'
(Other definitions for apace that I've seen before include "Swiftly, quickly" , "at high speed" , "(Move on) swiftly" , "fast" , "What's quickly" .)