Fashion centre with diamonds in reserve (9)
I believe the answer is:
reticence
'reserve' is the definition.
('reticence' can be a synonym of 'reserve')
'fashion centre with diamonds' is the wordplay.
'fashion' is an anagram indicator.
'with' is an insertion indicator.
'diamonds' becomes 'ice' (I've seen this before).
'centre' anagrammed gives 'retnce'.
'retnce' placed around 'ice' is 'RETICENCE'.
'in' acts as a link.
(Other definitions for reticence that I've seen before include "Tendency to be reserved in communication" , "Restraint" , "Shyness" , "modesty" , "Quality of being sparing in communication" .)