In street he's issuing paper (6)
I believe the answer is:
thesis
'paper' is the definition.
(I've seen this before)
'in street he's issuing' is the wordplay.
'in' indicates a hidden word.
'THESIS' is hidden in the letters of 'street hes issuing'.
(Other definitions for thesis that I've seen before include "Treatise advancing a new point of view resulting from research" , "Subject" , "Dissertation presented for a doctorate" , "Proposition" , "He sits (anag) - treatise" .)