Keen as __, Very Eager
Puzzle 5 of Spy World Medium Pack
Question is: Keen as __, Very Eager
and the answer is: MUSTARD
Word Meaning:
MUSTARD — A plant of certain species of the genus Brassica, or of related genera (especially Sinapis alba, in the family Brassicaceae, with yellow flowers, and linear seed pods).
Definitions from Wiktionary.