Gemstone set in rubbery leather (5)
I believe the answer is:
beryl
'gemstone' is the definition.
(beryl is a kind of gemstone)
'set in rubbery leather' is the wordplay.
'set in' indicates the answer is hidden within the clue.
'BERYL' is hidden in the letters of 'rubbery leather'.
(Other definitions for beryl that I've seen before include "Pale greenish" , "Girl" , "- Bainbridge, English novelist" , "Gemstone of which emerald is a variety" , "Coloured stone" .)