Bust a gut holding a deer (4)

I believe the answer is:

stag

'a deer' is the definition.
(I know that deer can be written as stag)

'bust a gut holding' is the wordplay.
'holding' indicates a hidden word.
'STAG' is hidden within 'bust a gut'.

(Other definitions for stag that I've seen before include "Male at party?" , "Men-only" , "One who speculates" , "Without women" , "Antlered animal" .)

I've seen this clue in the Sydney Morning Herald.

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