One thinks of a non-metric measure for a bra (5)
I believe the answer is:
brain
'one thinks of a non-metric' is the definition.
I can't tell whether this defines the answer.
'measure for a bra' is the wordplay.
'measure' becomes 'in' (in is a kind of measure).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'in' put after 'bra' is 'BRAIN'.
Can you help me to learn more?
(Other definitions for brain that I've seen before include "Organ of the intellect" , "It's in the skull" , "Intelligence" , "The grey matter" , "Hit hard; intellect" .)