Quickly, father turns a card (5)
I believe the answer is:
apace
'quickly' is the definition.
(I know that quickly can be written as apace)
'father turns a card' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'turns' says the letters should be written in reverse.
'a card' becomes 'ace' (ace is a type of playing card).
'pa' written backwards gives 'ap'.
'ap'+'ace'='APACE'
(Other definitions for apace that I've seen before include "(Move on) swiftly" , "What's quickly" , "At a rapid rate" , "Quick" , "at high speed" .)