Lead-in to fall (4)
I believe the answer is:
prat
'lead-in to fall' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for prat that I've seen before include "Wally" , "Rapt like silly ass" , "In slang, a fool" , "Stupid person" , "Incompetent idiot" .)