Caught short, going in toilet that’s cracked (4)
I believe the answer is:
loco
'cracked' is the definition.
('loco' can be a synonym of 'cracked')
'caught short going in toilet' is the wordplay.
'short' says to take the initial letters.
'going in' is an insertion indicator.
'toilet' becomes 'loo' (loo is a kind of toilet**).
The initial letter of 'caught' is 'c'.
'c' going into 'loo' is 'LOCO'.
'that's' acts as a link.
(Other definitions for loco that I've seen before include "with a screw loose?" , "Engine - nuts" , "Crazy; engine" , "Railway engine - mad!" , "Round the bend" .)