Sulphur taken by a boy as healthy food? (5)
I believe the answer is:
salad
'healthy food?' is the definition.
(I've seen this before)
'sulphur taken by a boy' is the wordplay.
'sulphur' becomes 'S' (synonyms).
'taken by' is a charade indicator (letters next to each other).
'boy' becomes 'lad' (informal term for boy).
's'+'a'+'lad'='SALAD'
'as' is the link.
(Other definitions for salad that I've seen before include "One may well be green" , "rabbit food" , "one gets dressed" , "A dish of lettuce and vegetables" , "Healthy dish" .)