Hold about: dull way of learning subject in food science (7)
I believe the answer is:
protein
'subject in food science' is the definition.
'hold about dull way of learning' is the wordplay.
'hold' becomes 'pin' (I can't justify this - if you can you should believe this answer much more).
'about' indicates putting letters inside.
'dull way of learning' becomes 'rote'.
'pin' going around 'rote' is 'PROTEIN'.
Can you help me to learn more?
(Other definitions for protein that I've seen before include "Combination of amino acids in living things" , "A body chemical; pointer (anag.)" , "Important component of diet" , "Important dietary component" , "Essential part of diet, found in meat, say" .)