Excursion taken in fall, perhaps (4)
I believe the answer is:
trip
'excursion' is the definition.
(I've seen this before)
'taken in fall perhaps' is the wordplay.
'taken in' is an insertion indicator.
'fall' becomes 'tip'.
'perhaps' becomes 'r' (I can't justify this - if you can you should believe this answer much more).
'tip' going around 'r' is 'TRIP'.
Can you help me to learn more?
(Other definitions for trip that I've seen before include "Device working a trap or alarm when stumbled over" , "blunder" , "often occurring just before the fall" , "Hallucinogenic drug experience - lose one's balance" , "Pleasure excursion" .)