Bridge that’s not finished well (3)
I believe the answer is:
spa
'well' is the definition.
(I've seen this in other clues)
'bridge that's not finished' is the wordplay.
'bridge' becomes 'span' (synonyms).
'that's not finished' means to remove the last letter.
'span' with its last letter removed is 'SPA'.
(Other definitions for spa that I've seen before include "Boston" , "well" , "A therapeutic hot spring" , "Water source" , "place of treatment" .)