Answer: spiff

AnswerCrossword Clue
SPIFF

Spruce (up)

SPIFF

Best-dressedness

SPIFF

.. up (make stylish)

SPIFF
Smarten (up)
SPIFF
.. up (improve the look of)
SPIFFAdorn, with "up"
SPIFF.. up (neaten)
SPIFFSplendid: Slang.
SPIFFNeaten, with "up"
SPIFFNeaten (up)
SPIFFCalvin's alter ego Spaceman ...
SPIFF... up (improve the look of)
SPIFFSalesman's reward, slangily
SPIFFSalesman's reward