Stifles curses about exercise (7)

I believe the answer is:

dampens

'stifles' is the definition.
('dampen' can be a synonym of 'stifle')

'curses about exercise' is the wordplay.
'curses' becomes 'damns' ('damn' can be a synonym of 'curse').
'about' is an insertion indicator.
'exercise' becomes 'pe' (Physical Education).
'damns' going around 'pe' is 'DAMPENS'.

I've seen this clue in the Sydney Morning Herald.

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