Trick with bottomless ravine (4)
I believe the answer is:
gull
'trick' is the definition.
(thesaurus)
'bottomless ravine' is the wordplay.
'bottomless' means to remove the last letter.
'ravine' becomes 'gully' (I've seen this before).
'gully' with its last letter taken away is 'GULL'.
'with' acts as a link.
(Other definitions for gull that I've seen before include "Fool - bird" , "Seabird - fool" , "Take in" , "Fool - hoax" , "A bird; to deceive" .)