Back massage involving student leads to confused impression (4)
I believe the answer is:
blur
'confused impression' is the definition.
(I've seen this before)
'back massage involving student' is the wordplay.
'back' says the letters should be written backwards.
'massage' becomes 'rub' (I've seen this before).
'involving' means one lot of letters goes inside another.
'student' becomes 'l'.
'rub' enclosing 'l' is 'rulb'.
'rulb' back-to-front is 'BLUR'.
'leads to' is the link.
(Other definitions for blur that I've seen before include "fade" , "Hazy or indistinct representation" , "Ill-defined smear" , "Indistinct appearance like smear" , "Fuzzy image" .)