Thinker thus gets boxes (8)
I believe the answer is:
socrates
'thinker' is the definition.
(I have seen 'Deep thinker' mean 'socrates' so perhaps 'thinker' could also mean 'socrates')
'thus gets boxes' is the wordplay.
'thus' becomes 'so' (synonyms).
'gets' is a charade indicator (letters next to each other).
'boxes' becomes 'crates' (crate is a kind of box).
'so'+'crates'='SOCRATES'
(Other definitions for socrates that I've seen before include "old question-master?" , "Philosophical Greek" , "Hemlocked philosopher" , "Legendary footballer" , "sage from Greece" .)