### Clue: Signal shown in flat, perhaps, by mayor (10)
### Answer: NOTEWORTHY 
 ### Explanation: Definition: Signal
  NOTE(in music, an example of which,perhaps, is the "flat", in contrast to a natural or sharp) **plus**(by) WORTHY(a person of eminent worth, merit or position, of which a mayor is presumably one). 
Answer: As an adjective of someone,something notable, outstanding.  Almost same in meaning to the adjective, worthy, in fact.