They happen -- in fact -- to struggle at first (6)
I believe the answer is:
events
'they happen' is the definition.
(I've seen this before)
'fact to struggle at first' is the wordplay.
'fact' becomes 'even' (I can't explain this - if you can you should give a lot more credence to this answer).
'at first' suggests taking the first letters.
The initial letters of 'to struggle' is 'ts'.
'even'+'ts'='EVENTS'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for events that I've seen before include "Things taking place" , "Important or notable happenings" , "Episodes" , "Incidents, occasions" , "Noteworthy happenings" .)