Very ill person in short top and a cape (7)
I believe the answer is:
cardiac
'very ill person' is the definition.
(someone with heart problems)
'short top and a cape' is the wordplay.
'short top' becomes 'cardia' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'a cape' becomes 'c' (abbreviation used on maps).
'cardia'+'c'='CARDIAC'
'in' acts as a link.
(Other definitions for cardiac that I've seen before include "one with a heart disorder" , "Of the heat, perhaps illness" , "Pertaining to the heart" , "Physiologically, of the heart" , "Sort of surgery" .)