Answer:

enthusiast

Answer	Crossword Clue
ENTHUSIAST	Nut
ENTHUSIAST	Buff
ENTHUSIAST	Gung-ho sort

ENTHUSIAST	Devotee.
ENTHUSIAST	She's a nut, it turns out! (10)

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.