Moralist capturing exposed criminal (7)
I believe the answer is:
puritan
'moralist' is the definition.
(I've seen this before)
'capturing exposed criminal' is the wordplay.
'exposed' indicates the central letters (outside letters removed).
'criminal' indicates anagramming the letters.
The middle letters of 'capturing' are 'apturin'.
'apturin' anagrammed gives 'PURITAN'.
(Other definitions for puritan that I've seen before include "very proper person?" , "Over-strict moralist" , "narrow-minded" , "Person of extremely strict morals" , "Member of a group of English Protestants who thought that the Protestant Reformation was incomplete" .)