Stupidly trail round district of Venice (6)
I believe the answer is:
rialto
'district of venice' is the definition.
(I've seen this before)
'stupidly trail round' is the wordplay.
'stupidly' indicates anagramming the letters.
'round' becomes 'o' (round can mean a round object).
'trail' with letters rearranged gives 'rialt'.
'rialt'+'o'='RIALTO'
(Other definitions for rialto that I've seen before include "Island in Venice with famous bridge" , "Central area of Venice and suburb of Dublin" , "business centre" , "Venetian district" , "Region in Venice and Dublin" .)