Occasionally thwart bowler? (3)

I believe the answer is:

hat

'bowler?' is the definition.
(thesaurus)

'occasionally thwart' is the wordplay.
'occasionally' indicates alternate letters.
The alternating letters of 'thwart' are 'HAT'.

(Other definitions for hat that I've seen before include "e.g. Pork pie" , "Headwear" , "Headdress" , "Lid" , "Cap" .)

I've seen this clue in The Times.

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