Substance with large molecules put back on my cut (7)
I believe the answer is:
polymer
'substance with large molecules' is the definition.
I can't judge whether this defines the answer.
'back on my cut' is the wordplay.
'back' is a reversal indicator.
'on' becomes 're' ('on' can be mean 'with reference to').
'cut' becomes 'lop' (lopping is a kind of cutting).
're'+'my'+'lop'='remylop'
'remylop' back-to-front is 'POLYMER'.
'put' acts as a link.
Can you help me to learn more?
(Other definitions for polymer that I've seen before include "Substance such as nylon" , "Substance with large molecules of smaller units" , "Eg, protein, rubber etc." , "Mo, reply to the large molecule" , "Repeated-molecule compound" .)