Unfortunately kisses can leave a malady (8)
I believe the answer is:
sickness
'malady' is the definition.
(I know that malady can be written as sickness)
'unfortunately kisses can leave a' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'leave' is a deletion indicator.
'kisses'+'can'='kissescan'
'kissescan' with 'a' taken away is 'kissescn'.
'kissescn' with letters rearranged gives 'SICKNESS'.
(Other definitions for sickness that I've seen before include "Illness, disease" , "It's not looking good" , "State of being ill" , "Illness, malady" , "Ill health" .)