Crossword Genius

Like mounted horse, most cap­ably controlled by jockey (10)

Ross

I believe the answer is:

bestridden

'like mounted horse' is the definition.
(a past-tense form of bestride)

'most capably controlled by jockey' is the wordplay.
'most capably' becomes 'best'.
'controlled by jockey' becomes 'ridden'.
'best'+'ridden'='BESTRIDDEN'

(Other definitions for bestridden that I've seen before include "As ponies may be" , "defended" .)

I've seen this clue in The Guardian.
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