Errant knight in huge trouble (7)
I believe the answer is:
unhinge
'trouble' is the definition.
(unhinging is a kind of troubling)
'errant knight in huge' is the wordplay.
'errant' indicates an anagram (I've seen this in other clues).
'knight' becomes 'n' (chess).
'n'+'in'+'huge'='ninhuge'
'ninhuge' with letters rearranged gives 'UNHINGE'.
(Other definitions for unhinge that I've seen before include "Remove a door - or drive insane" , "Drive mad in huge inn" , "Make mentally unbalanced" , "Drive demented in huge inn" , "Unbalance mentally" .)