Tack into wind, beginning to raise sail (9)
I believe the answer is:
spinnaker
'sail' is the definition.
(I know that spinnaker is a type of headsail)
'tack into wind beginning to raise' is the wordplay.
'tack' becomes 'pin' (a tack is a nail or pin).
'into' means one lot of letters goes inside another.
'wind' becomes 'snake' (snaking is a kind of winding).
'beginning to' says to take the initial letters.
The first letter of 'raise' is 'r'.
'pin' placed inside 'snake' is 'spinnake'.
'spinnake'+'r'='SPINNAKER'
(Other definitions for spinnaker that I've seen before include "Type of sail" , "Lightweight sail" , "Large racing sail" , "Large three-cornered sail" , "an expanse of cloth" .)