College ordered steer in resin (9)
I believe the answer is:
polyester
'resin' is the definition.
(I know that polyester is a type of synthetic resin)
'college ordered steer in' is the wordplay.
'college' becomes 'poly' (polytechnic).
'ordered' indicates anagramming the letters.
'in' means one lot of letters goes inside another.
'steer' is an anagram of 'ester'.
'poly' inserted within 'ester' is 'POLYESTER'.
(Other definitions for polyester that I've seen before include "Man-made fibre" , "material found in fabrics" , "This material goes out to Presley" , "Textile material" , "Synthetic fibre or substance" .)