Enter without payment: takings collapse (9)
I believe the answer is:
gatecrash
'enter' is the definition.
(gatecrashing is a kind of entering)
'takings collapse' is the wordplay.
'takings' becomes 'gate' (I can't explain this - if you can you should believe this answer much more).
'collapse' becomes 'crash' (synonyms).
'gate'+'crash'='GATECRASH'
'without payment' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for gatecrash that I've seen before include "join party if not wanted" , "join party unofficially" , "Try to get in for free" , "enter without invitation" , "to do so uninvited" .)