Son caught hospital department's smells (6)
I believe the answer is:
scents
'smells' is the definition.
(scent is a kind of smell)
'son caught hospital department's' is the wordplay.
'son' becomes 's'.
'caught' becomes 'c' (cricket abbreviation).
'hospital department's' becomes 'ents'.
's'+'c'+'ents'='SCENTS'
(Other definitions for scents that I've seen before include "Essences and perfumes" , "Trails" , "Distinctive odours, usually pleasant" , "Fragrances, smells" .)