Hopeful boy is getting into drink dispenser (10)
I believe the answer is:
optimistic
'hopeful' is the definition.
(I've seen this before)
'boy is getting into drink dispenser' is the wordplay.
'boy' becomes 'tim' (**).
'getting into' is an insertion indicator.
'drink dispenser' becomes 'optic' (I've seen this before).
'tim'+'is'='timis'
'timis' going within 'optic' is 'OPTIMISTIC'.
(Other definitions for optimistic that I've seen before include "Happy-go-lucky" , "Hopeful and confident" , "Pollyannaish" , "Looking on the bright side" , "Hopeful about the future" .)