Devoted to razor-sharp side on field (4,2)

I believe the answer is:

keen on

'devoted to' is the definition.
(if you're keen on something you're devoted to it)

'razor-sharp side on field' is the wordplay.
'razor-sharp' becomes 'keen' (I've seen this in another clue).
'side on field' becomes 'on' (leg side in cricket).
'keen'+'on'='KEEN ON'

I've seen this clue in The Guardian.

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