Gem held between rubbery lips (5)
I believe the answer is:
beryl
'gem' is the definition.
(beryl is a kind of gem)
'held between rubbery lips' is the wordplay.
'held' indicates the answer is hidden within the clue.
'BERYL' is hidden within 'between rubbery lips'.
(Other definitions for beryl that I've seen before include "Gemstone (for Ms Bainbridge?)" , "- - Bainbridge (lit.)" , "Transparent mineral used as a gemstone" , "- Bainbridge, English novelist" , "Girl's name - gemstone" .)