Collar American nicking rare complete works (6)
I believe the answer is:
corpus
'complete works' is the definition.
(complete collection of texts)
'collar american nicking rare' is the wordplay.
'collar' becomes 'cop' (both can mean to apprehend or catch).
'american' becomes 'us' (abbreviation for United States).
'nicking' is an insertion indicator (I've seen this in other clues).
'rare' becomes 'r' (listed by Oxford Dictionary of Abbreviations).
'cop'+'us'='copus'
'copus' going around 'r' is 'CORPUS'.
(Other definitions for corpus that I've seen before include "Collection of author's works" , "collection of literature" , "college" , "A body as of writings" , "text collection" .)