Claimed to be involved with drugs (7)
I believe the answer is:
medical
'with drugs' is the definition.
(with medical drugs)
'claimed to be involved' is the wordplay.
'to be involved' is an anagram indicator (involved can mean confusing or complex).
'claimed' is an anagram of 'MEDICAL'.
(Other definitions for medical that I've seen before include "Examination of physical health" , "Relating to the art of healing" , "Check-up - declaim (anag)" , "Relating to treatment rather than surgery" , "Doctor's test" .)