A city boss’s conclusion, sad to say (4)
I believe the answer is:
alas
'sad to say' is the definition.
(I've seen this before)
'a city boss's conclusion' is the wordplay.
'city' becomes 'la' (Los Angeles).
'conclusion' suggests the final letters.
The final letter of 'bosss' is 's'.
'a'+'la'+'s'='ALAS'
(Other definitions for alas that I've seen before include "Woeful expression" , "I'm sorry to say" , "Sadly, unfortunately" , "Exclamation of grief" , "Regrettably, unfortunately" .)