Expert grabbing old man quickly (5)
I believe the answer is:
apace
'quickly' is the definition.
(I know that quickly can be written as apace)
'expert grabbing old man' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'grabbing' indicates putting letters inside.
'old man' becomes 'pa' (both can mean father).
'ace' going around 'pa' is 'APACE'.
(Other definitions for apace that I've seen before include "What's quickly" , "(Move on) swiftly" , "At a rapid rate" , "at high speed" , "Quick" .)