Fifty young foxes all round - but only thirteen in the pack! (5)
I believe the answer is:
clubs
'the pack' is the definition.
(thesaurus)
'fifty young foxes all round' is the wordplay.
'fifty' becomes 'L' (Roman numeral).
'young foxes' becomes 'cubs' (I've seen this before).
'all round' indicates putting letters inside.
'l' placed into 'cubs' is 'CLUBS'.
'but only thirteen in' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for clubs that I've seen before include "playing cards" , "Card suit" , "Heavy sticks; association" , "Associations of people with similar interests" , "discos" .)