Delilah doesn't get ill from start (4)

I believe the answer is:

head

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'start' is the definition.
('head start' can be a synonym of 'start')

I can't explain the rest of the clue.

(Other definitions for head that I've seen before include "Chief; bonce" , "Promontory; foam" , "Skull" , "See 25" , "See 14" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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