Underwear as present — for the most part found by a student in MS (8)
I believe the answer is:
thermals
'underwear' is the definition.
(I know that thermals is a type of underwear)
'the most part found by a student in ms' is the wordplay.
'most part' becomes 'r' (I am not sure about this - if you are sure you should believe this answer much more).
'found by' says to put letters next to each other.
'student' becomes 'l' (as in L-plates for learner drivers).
'in' indicates putting letters inside.
'a'+'l'='al'
'al' going inside 'ms' is 'mals'.
'the'+'r'+'mals'='THERMALS'
'as present for' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
(Other definitions for thermals that I've seen before include "Warm underwear" , "Upward air currents - winter warmers" , "Lest harm come to rising currents of air" , "Rising currents of hot air" , "Warm clothes" .)