On the outside, with no kiss, forever (9)
I believe the answer is:
eternally
'forever' is the definition.
(I know that forever can be written as eternally)
'on the outside with no kiss' is the wordplay.
'on the outside' becomes 'externally' (synonyms).
'with no' is a deletion indicator.
'kiss' becomes 'x' (X can represent a kiss).
'externally' with 'x' taken out is 'ETERNALLY'.
(Other definitions for eternally that I've seen before include "Nearly let out forever" , "For evermore" , "Always and ever" , "constantly" , "Always and forever" .)