Check on form (8)

I believe the answer is:

restrain

'check' is the definition.
(I know that check is a kind of restrain)

'on form' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'form' becomes 'strain' (synonyms).
're'+'strain'='RESTRAIN'

(Other definitions for restrain that I've seen before include "Keep in check" , "Manacle" , "Tie up - arrest" , "Keep under control" , "Hold back, tether" .)

I've seen this clue in The Telegraph.

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