After ingesting cocaine, favoured examination of the chest (8)
I believe the answer is:
pectoral
'of the chest' is the definition.
(I've seen this before)
'after ingesting cocaine favoured examination' is the wordplay.
'after ingesting' means one lot of letters goes inside another.
'cocaine' becomes 'C' (drugs abbreviation).
'favoured' becomes 'pet' (as in a pet project).
'examination' becomes 'oral' (oral examination is a kind of examination).
'c' inserted inside 'pet' is 'pect'.
'pect'+'oral'='PECTORAL'
(Other definitions for pectoral that I've seen before include "sort of cross" , "Relating to the breast or chest" , "(Large muscle) of the chest" , "Alert cop about chest" , "Of the chest or breast, like muscles" .)