Deep and dim mix was hindered (7)
I believe the answer is:
impeded
'hindered' is the definition.
('impede' can be a synonym of 'hinder')
'deep and dim mix' is the wordplay.
'and' says to put letters next to each other.
'mix' is an anagram indicator.
'deep' after 'dim' is 'dimdeep'.
'dimdeep' is an anagram of 'IMPEDED'.
'was' acts as a link.
(Other definitions for impeded that I've seen before include "Hampered" , "Hindered progress" , "Blocked (progress)" , "Got in the way of" , "Obstructed" .)