Busy man caught twitch (6)
I believe the answer is:
hectic
'busy' is the definition.
(thesaurus)
'man caught twitch' is the wordplay.
'man' becomes 'he'.
'caught' becomes 'c' (cricket abbreviation).
'twitch' becomes 'tic' (tic is a kind of twitch).
'he'+'c'+'tic'='HECTIC'
(Other definitions for hectic that I've seen before include "Bustling" , "Frenetic" , "Full of frantic activity" , "Marked by intense agitation - fevered" , "Frantically active" .)