Answer:

rosin

Answer	Crossword Clue
ROSIN	Fiddler's need
ROSIN	Prepare a bow
ROSIN	Bow balm

ROSIN	It makes ballet slippers non-slip
ROSIN	Pine tree sap
ROSIN	Pitching mound bag
ROSIN	Bow application
ROSIN	Violin-bow coater
ROSIN	Violinist's aid
ROSIN	32-Down's need
ROSIN	It's in the bag, on the mound

ROSIN	Mound bag contents
ROSIN	Pro bowler's supply
ROSIN	Violinist's supply
ROSIN	Pitcher's gripping aid
ROSIN	Pitcher's bagful
ROSIN	Violinist's accessory
ROSIN	Use this to whip grip slip
ROSIN	Violinist's rub

ROSIN	Powder for a violin bow
ROSIN	... bag
ROSIN	Bag contents on the mound
ROSIN	Need for some virtuosos
ROSIN	Violin-bow coating
ROSIN	Substance for a violin bow
ROSIN	Violin string application
ROSIN	Pitcher's need

ROSIN	Cellist's need
ROSIN	Bow coating
ROSIN	Pine product
ROSIN	Cellist's purchase
ROSIN	Pitcher's grip improver
ROSIN	Violinist's need
ROSIN	Bower buy
ROSIN	String accessory

ROSIN	Bagful of diamonds
ROSIN	Violin bow coating
ROSIN	Bow movement aid
ROSIN	Stern-to-bow application
ROSIN	Fiddle sticker?