Judicious puritan not disheartened (7)
I believe the answer is:
prudent
'judicious' is the definition.
(similar in meaning)
'puritan not disheartened' is the wordplay.
'puritan' becomes 'prude' (synonyms).
'disheartened' means to remove the middle letters.
'not' with its centre taken out is 'nt'.
'prude'+'nt'='PRUDENT'
(Other definitions for prudent that I've seen before include "not taking any risks?" , "Cautious; discreet" , "caution" , "Cautious and circumspect" , "Careful, circumspect" .)