Start being involved (5)
I believe the answer is:
begin
'start' is the definition.
('begin' can be a synonym of 'start')
'being involved' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'being' is an anagram of 'BEGIN'.
(Other definitions for begin that I've seen before include "former Israeli Nobel peace prize winner" , "Monachem --" , "Clandestine, furtive" , "Initiate" , "Found" .)