Gemstone for every single girl (7)
I believe the answer is:
peridot
'gemstone' is the definition.
(I know that peridot is a type of transparent gem)
'every single girl' is the wordplay.
'every' becomes 'per' ('per' means 'for each' or 'for every').
'single' becomes 'I' (one).
'girl' becomes 'dot' ().
'per'+'i'+'dot'='PERIDOT'
'for' is the link.
(Other definitions for peridot that I've seen before include "Pale green gemstone" , "olivine" , "Top ride (anag) - gemstone" , "mineral" , "A green semi-precious stone" .)