Sail bark regularly, wearing bowler (9)
I believe the answer is:
spinnaker
'sail' is the definition.
(I know that spinnaker is a type of sail)
'bark regularly wearing bowler' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'wearing' is an insertion indicator.
'bowler' becomes 'spinner' (a spinner is a kind of bowler in cricket).
The alternating letters of 'bark' are 'ak'.
'ak' placed inside 'spinner' is 'SPINNAKER'.
(Other definitions for spinnaker that I've seen before include "Large three-cornered sail" , "Large racing sail" , "one using the breeze" , "Lightweight sail" , "Large triangular sail at the front of a yacht" .)