Student leaves stupid call smiling inanely (9)
I believe the answer is:
simpering
'smiling inanely' is the definition.
'simpering' can be an answer for 'smiling' (simpering is a kind of smiling). I'm unsure of the 'inanely' bit.
'student leaves stupid call' is the wordplay.
I cannot quite see how this works, but
'call' could be 'ring' (telephone call) and 'ring' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for simpering that I've seen before include "behaving affectedly" , "Smiling in an affected and silly way" .)