The Italian reclines in street — most stupid (8)
I believe the answer is:
silliest
'most stupid' is the definition.
(I've seen this before)
'the italian reclines in street' is the wordplay.
'the italian' becomes 'il' ('the' in Italian).
'reclines' becomes 'lies' (I've seen this before).
'in' indicates putting letters inside.
'street' becomes 'st'.
'il'+'lies'='illies'
'illies' inserted within 'st' is 'SILLIEST'.
(Other definitions for silliest that I've seen before include "It's Ellis (anag)" , "Most stupid" , "Most unwise" , "Most inane" , "Most foolish" .)