Bust a gut containing party of lads

I believe the answer is:

stag

I'm a little stuck... Click here to teach me more about this clue!

'party of lads' is the definition.
'stag' can be an answer for 'party' (stag party is a kind of party). I am not certain of the 'of lads' bit.

'bust a gut containing' is the wordplay.
'containing' indicates a hidden word (I've seen 'contains' mean this).
'STAG' can be found hidden inside 'bust a gut'.

Can you help me to learn more?

(Other definitions for stag that I've seen before include "Adult male deer, often with antlers" , "animal of the deer family" , "American party" , "speculator wanting quick profit" , "Deer; with only men" .)

I've seen this clue in The Irish Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.