Veteran of theatre in gilded bar opening last of Bollinger ... (3,6)
I believe the answer is:
old stager
'veteran' is the definition.
(I know that veteran can be written as old stager)
'theatre in gilded bar opening last of bollinger' is the wordplay.
'theatre' becomes 'stage' (stage is a kind of theatre).
'in' indicates putting letters inside.
'gilded' becomes 'gold' (synonyms).
'bar opening' means to remove the first letter (the word except or bar its opening letter).
'last of' suggests the final letters.
The final letter of 'bollinger' is 'r'.
'gold' with its initial letter taken off is 'old'.
'old'+'r'='oldr'
'stage' going inside 'oldr' is 'OLD STAGER'.
'of' acts as a link.
(Other definitions for old stager that I've seen before include "senior citizen" , "expert" , "veteran" , "One who's experienced a lot" .)