Substance in concentrated extract (7)
I believe the answer is:
essence
This clue is a double definition.
'substance' is the first definition.
(synonyms)
'concentrated extract' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for essence that I've seen before include "Inner nature of anything" , "Indispensable" , "A thing's intrinsic nature" , "Intrinsic nature; four Dn" , "Intrinsic nature (of something)" .)