The deficient retail supply (8,7)
I believe the answer is:
definite article
'the' is the definition.
'deficient retail supply' is the wordplay.
'supply' indicates anagramming the letters (supply of letters to make).
'deficient'+'retail'='deficientretail'
'deficientretail' anagrammed gives 'DEFINITE ARTICLE'.
(Other definitions for definite article that I've seen before include "part of speech" , "Maybe the" , "In English, it's always the" , "Black and white feature in paper" .)