Channel dominated essentially by darts (7)
I believe the answer is:
narrows
'channel' is the definition.
(I know that narrow is a type of channel)
'dominated essentially by darts' is the wordplay.
'essentially' means to look at the middle letters.
'by' means one lot of letters go next to another.
'darts' becomes 'arrows' (I've seen this before).
The middle letter of 'dominated' is 'n'.
'n'+'arrows'='NARROWS'
(Other definitions for narrows that I've seen before include "Part of River" , "Confined channel" , "Constricts" , "Reduces in width" , "Gets smaller in width" .)