Fellow caught twitch when busy (6)
I believe the answer is:
'busy' is the definition.
'fellow caught twitch' is the wordplay.
'fellow' becomes 'he' ('he' refers to a man).
'caught' becomes 'c' (cricket abbreviation).
'twitch' becomes 'tic' (tic is a kind of twitch).
'when' is the link.
(Other definitions for hectic that I've seen before include "Agitated and rushed" , "Frantically active" , "Involving feverish activity, flushed" , "Bustling" , "Full of frantic activity" .)