Nothing stops search in ravine (5)
I believe the answer is:
coomb
'ravine' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I can't see?
'nothing stops search' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'stops' indicates putting letters inside (stopping can mean blocking a gap).
'search' becomes 'comb' (combing is a kind of searching).
'o' placed inside 'comb' is 'COOMB'.
'in' is the link.
Can you help me to learn more?
(Other definitions for coomb that I've seen before include "Short valley or hollow" , "Hollow on hill" , "Hillside valley or hollow" .)