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.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'relaxed into gs role at last' is the subsidiary indication.
'relaxed' becomes 'limp' (**).
'into' indicates putting letters inside.
'at last' indicates one should take the final letters.
The last letter of 'role' is 'e'.
'limp' inserted inside '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".)