Rejects diamonds one store initially has (7)
I believe the answer is:
disowns
'rejects' is the definition.
(to disown is to reject or spurn)
'diamonds one store initially has' is the wordplay.
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'one' becomes 'I' (Roman numeral).
'initially' says to take the initial letters.
'has' becomes 'owns' ('own' can be a synonym of 'have').
The initial letter of 'store' is 's'.
'd'+'i'+'s'+'owns'='DISOWNS'
(Other definitions for disowns that I've seen before include "Refuses to acknowledge" , "Has nothing to do" .)