Essence in tea urn, brewed (6)
I believe the answer is:
nature
'essence' is the definition.
(I've seen this before)
'tea urn brewed' is the wordplay.
'brewed' indicates anagramming the letters.
'tea'+'urn'='teaurn'
'teaurn' anagrammed gives 'NATURE'.
'in' is the link.
(Other definitions for nature that I've seen before include "type?" , "Character, make-up" , "Essence; kind" , "Picturesque countryside" , "Essential character" .)