Something like obesity forcing MB into open (10)
I believe the answer is:
embonpoint
'something like obesity' is the definition.
(embonpoint can mean plumpness)
'forcing mb into open' is the wordplay.
'forcing' indicates anagramming the letters.
'mb'+'into'+'open'='mbintoopen'
'mbintoopen' anagrammed gives 'EMBONPOINT'.
(Other definitions for embonpoint that I've seen before include "stout" , "Stoutness" .)