Gold collars with raised stitching, to a disgusting extent (2,7)
I believe the answer is:
ad nauseam
'to a disgusting extent' is the definition.
(I've seen this before)
'gold collars with raised stitching' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'collars' is an insertion indicator (to collar can mean to apprehend or capture).
'with' becomes 'and'.
'raised' says the letters should be written in reverse (going up in a down clue).
'stitching' becomes 'seam' (I am not sure about this - if you are sure you should believe this answer much more).
'and' back-to-front is 'dna'.
'au' placed around 'dna' is 'adnau'.
'adnau'+'seam'='AD NAUSEAM'
Can you help me to learn more?
(Other definitions for ad nauseam that I've seen before include "Past the stage of enjoying" , "Interminably" , "To a disgusting extent" , "To a disgusting degree" , "To a very tiresome degree" .)