Scots dress student in gear (4)
I believe the answer is:
kilt
'scots dress' is the definition.
(I've seen this before)
'student in gear' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'in' indicates putting letters inside.
'gear' becomes 'kit' (kit is a kind of gear).
'l' going into 'kit' is 'KILT'.
(Other definitions for kilt that I've seen before include "Part of Highland dress" , "Checked menswear" , "Scottish garb" , "Scotsman's garb" , "Under which, traditionally, a Scotsman wears nothing" .)