Clean inside of gondola, underneath bridge (7)
I believe the answer is:
launder
'clean' is the definition.
(laundering is a kind of cleaning)
'of gondola underneath bridge' is the wordplay.
'of' indicates the answer is hidden within the clue.
'LAUNDER' can be found hidden inside 'gondola underneath bridge'.
'inside' acts as a link.
(Other definitions for launder that I've seen before include "Wash and iron linen" , "Make clean, clothing or money" , "Wash or cleanse, clothes or money" , "Perhaps decriminalise" , "Led a run (anag)" .)