Marked lack of cuddling partner (5)
I believe the answer is:
noted
'marked' is the definition.
('note' can be a synonym of 'mark')
'lack of cuddling partner' is the wordplay.
'lack of' becomes 'no' (lack of money is no money).
'cuddling partner' becomes 'ted' (teddy bear).
'no'+'ted'='NOTED'
(Other definitions for noted that I've seen before include "Significant" , "Famed" , "Observed - recorded" , "Celebrity" , "remarked upon" .)