It's essentially fragrant (5)
I believe the answer is:
attar
'it's essentially fragrant' is the definition.
I can't tell whether this defines the answer.
'it's essentially fragrant' is the wordplay.
'it's' becomes 'atta' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'essentially' says to take the centre.
'fragrant' becomes 'odorous' (similar in meaning).
The centre of 'odorous' is 'r'.
'atta'+'r'='ATTAR'
Can you help me to learn more?
(Other definitions for attar that I've seen before include "Send out roses" , "Fragrant essence usually associated with the damask rose" , "Essential oil from flowers" , "Essential oil from flower" , "Oil from flowers for perfume" .)