Make a big effort to completely get the joke (4,1,3)
I believe the answer is:
bust a gut
'make a big' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'effort to completely get the joke' is the wordplay.
I cannot really understand how this works, but
'effort' could be 'tag' (tag is a kind of effort) and 'tag' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bust a gut that I've seen before include "Try really hard (slang)" , "Make a strenuous effort" , "Really work extra hard" , "Give it everything" , "Work extra hard to achieve something" .)