New darts channel (7)
I believe the answer is:
narrows
'channel' is the definition.
(thesaurus)
'new darts' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'darts' becomes 'arrows' (I've seen this before).
'n'+'arrows'='NARROWS'
(Other definitions for narrows that I've seen before include "Thin straits connecting two bodies of water" , "stretch of river" , "Confined channel" , "Reduces in width" , "Becomes less wide" .)