Synthetic substance found in college that's simmering at heart (7)
I believe the answer is:
polymer
'synthetic' is the definition.
(thesaurus)
'college that's simmering at heart' is the wordplay.
'college' becomes 'poly' (polytechnic).
'that's simmering' becomes 'simmering'.
'at heart' indicates the central letters.
The central letters of 'simmering' are 'mer'.
'poly'+'mer'='POLYMER'
'substance found in' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for polymer that I've seen before include "Material" , "Repeated-molecule compound" , "Compound with large molecules in simple repeated units" , "Mo, reply to the large molecule" , "Substance with large molecules of smaller units" .)