Untidy writing from last in class, creep (6)
I believe the answer is:
scrawl
'untidy writing' is the definition.
(I've seen this before)
'last in class creep' is the wordplay.
'last in' says to take the final letters.
'creep' becomes 'crawl' ('crawl' can be a synonym of 'creep').
The final letter of 'class' is 's'.
's'+'crawl'='SCRAWL'
'from' acts as a link.
(Other definitions for scrawl that I've seen before include "Write clumsily, hardly legible" , "Hasty writing" , "Untidy writing" , "Write in slovenly manner" , "Write hastily" .)