In Siberia, by small crevasse (5)
I believe the answer is:
abysm
'crevasse' is the definition.
(thesaurus)
'in siberia by small' is the wordplay.
'in' indicates a hidden word.
'ABYSM' is hidden in the letters of 'siberia by small'.
(Other definitions for abysm that I've seen before include "Deep hole" , "Bottomless pit" , "Deep cavity (arch)" , "Hell" , "Gorge" .)