Confused on diet, be submissive (8)
I believe the answer is:
obedient
'submissive' is the definition.
('obedient' is associated in meaning with 'submissive')
'confused on diet be' is the wordplay.
'confused' indicates an anagram.
'on'+'diet'+'be'='ondietbe'
'ondietbe' anagrammed gives 'OBEDIENT'.
(Other definitions for obedient that I've seen before include "Docile" , "Ready to comply" , "Complying with orders" , "Following instructions" , "Passive" .)