Maturing cheese, finally kept in inn, with odour (9)
I believe the answer is:
pubescent
'maturing' is the definition.
(going through puberty)
'cheese finally kept in inn with odour' is the wordplay.
'finally' indicates one should take the final letters.
'kept in' means one lot of letters goes inside another.
'inn' becomes 'pub' (both can mean a drinking establishment).
'with' means one lot of letters go next to another.
'odour' becomes 'scent' (synonyms).
The last letter of 'cheese' is 'e'.
'pub'+'scent'='pubscent'
'e' going inside 'pubscent' is 'PUBESCENT'.
(Other definitions for pubescent that I've seen before include "Just beginning sexual maturity" , "Young" , "Approaching a teenager" , "Getting down" .)