Disorderly time in college, extremely dingy (6)
I believe the answer is:
untidy
'disorderly' is the definition.
('untidy' can be similar in meaning to 'disorderly')
'time in college extremely dingy' is the wordplay.
'time' becomes 't'.
'in' means one lot of letters goes inside another.
'college' becomes 'uni' (I've seen this in other clues**).
'extremely' suggests removing the centre.
'dingy' with its centre taken out is 'dy'.
't' inserted within 'uni' is 'unti'.
'unti'+'dy'='UNTIDY'
(Other definitions for untidy that I've seen before include "Disorderly, sloppy" , "in a state" , "Slovenly, unkempt" , "missing order" , "Disorderly, dishevelled" .)