Implicate unfortunate Mercian in it? (11)
I believe the answer is:
incriminate
'implicate' is the definition.
(thesaurus)
'unfortunate mercian in it?' is the wordplay.
'unfortunate' indicates an anagram.
'mercian'+'in'+'it'='mercianinit'
'mercianinit' with letters rearranged gives 'INCRIMINATE'.
(Other definitions for incriminate that I've seen before include "Make to look guilty" , "Make someone appear guilty" .)