Profitable vital cure is synthesised (9)
I believe the answer is:
lucrative
'profitable' is the definition.
(similar in meaning)
'vital cure is synthesised' is the wordplay.
'is synthesised' is an anagram indicator.
'vital'+'cure'='vitalcure'
'vitalcure' is an anagram of 'LUCRATIVE'.
(Other definitions for lucrative that I've seen before include "Moneymaking" , "Revictual (anag.)" , "Producing a sizeable profit" , "Well-paid" , "Making money" .)