Replace ace, consider collecting diamonds (9)
I believe the answer is:
supersede
'replace' is the definition.
(synonyms)
'ace consider collecting diamonds' is the wordplay.
'ace' becomes 'super' (synonyms).
'consider' becomes 'see' (synonyms).
'collecting' indicates putting letters inside.
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'see' placed around 'd' is 'sede'.
'super'+'sede'='SUPERSEDE'
(Other definitions for supersede that I've seen before include "Stop using" , "Take the place of, override" , "Take the place of, supplant" , "set aside" , "Supplant, replace" .)