Backchat over identity of fatty material (5)
I believe the answer is:
lipid
'fatty material' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'backchat over identity' is the wordplay.
'backchat' becomes 'lip' (I've seen this in other clues).
'over' says to put letters next to each other (in a down clue, some letters go over others).
'identity' becomes 'id' (abbreviation).
'lip'+'id'='LIPID'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for lipid that I've seen before include "Insoluble fatty acid" , "fat, perhaps" , "One of the essential structural components of living cells" , "Organic compound" , "fatty stuff" .)