Heart attack caused by short knitted sweater worn with air conditioning (7)
I believe the answer is:
cardiac
'heart' is the definition.
(I've seen this before)
'worn with air conditioning' is the wordplay.
'worn with' becomes 'cardi' (I can't explain this - if you can you should believe this answer much more).
'air conditioning' becomes 'AC'.
'cardi'+'ac'='CARDIAC'
'attack caused by short knitted sweater' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for cardiac that I've seen before include "Of the heat, perhaps illness" , "Pertaining to the heart" , "Relating to the heart" , "one with a heart disorder" , "of hearts" .)