Observe opponents at bridge under obligation (8)

I believe the answer is:

beholden

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'under obligation' is the definition.
(thesaurus)

'observe opponents' is the wordplay.
'observe' becomes 'behold' (I've seen this before).
'opponents' becomes 'en' (I've seen this in other clues).
'behold'+'en'='BEHOLDEN'

'at bridge' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for beholden that I've seen before include "Under an obligation" , "Owing thanks, indebted" , "Obliged" , "Bound" , "Owing gratitude (to)" .)

I've seen this clue in The Daily Mail.

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