Student opening pencil case containing green spread (6)
I believe the answer is:
sprawl
'spread' is the definition.
(I know that sprawl is a kind of spread)
'student opening pencil case containing green' is the wordplay.
'opening' indicates taking the first letters.
'case' says to hollow out the word (remove centre letters).
'containing' is an insertion indicator.
'green' becomes 'raw' (both can mean naive or inexperienced).
'pencil' with its centre taken out is 'pl'.
The first letter of 'student' is 's'.
'pl' placed around 'raw' is 'prawl'.
's'+'prawl'='SPRAWL'
(Other definitions for sprawl that I've seen before include "Sit or lie with limbs spread out" , "Lounge" , "Spread out in ungainly way" , "Lie in an ungainly fashion" , "Lie about in loose-limbed manner" .)