Hard rubber from Spain - it penetrates bone (7)
I believe the answer is:
ebonite
'hard rubber' is the definition.
(synonyms)
'spain it penetrates bone' is the wordplay.
'spain' becomes 'e' (abbreviation for Espana).
'penetrates' means one lot of letters goes inside another.
'it' placed inside 'bone' is 'bonite'.
'e'+'bonite'='EBONITE'
'from' acts as a link.
(Other definitions for ebonite that I've seen before include "Rubbery material" , "Vulcanite" , "Bee on it (anag.)" , "something rubbery" , "vulcanised rubber" .)