Butcher's relaxed into G&S role at last (7)
I believe the answer is:
Here is my best explanation:
'butcher's' is the definition.
(butcher's [hook] is rhyming slang for a look)
'relaxed into gs role at last' is the wordplay.
'relaxed' becomes 'limp' (**).
'into' means one lot of letters goes inside another.
'at last' suggests the final letters.
The final letter of 'role' is 'e'.
'limp' inserted into 'gs' is 'glimps'.
(Other definitions for glimpse that I've seen before include "Briefly catch sight of", "Peek", "Gander", "Brief look", "Brief sight", "spot", "Fleeting vision", "Quick look", "Catch brief sight of" and "Notice".)