Lass around when love gives gemstone (7)
I believe the answer is:
girasol
'gemstone' is the definition.
(girasol is a kind of gemstone)
'lass around when love' is the wordplay.
'lass' becomes 'girl' (I've seen this before).
'around' means one lot of letters goes inside another.
'when' becomes 'as'.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'as'+'o'='aso'
'girl' placed around 'aso' is 'GIRASOL'.
'gives' acts as a link.
(Other definitions for girasol that I've seen before include "luminescent stone" , "Jewel" , "opal" , "yellow flower" , "Gem" .)