Yearly book; plant (6)
I believe the answer is:
annual
I believe this clue is a double definition.
'yearly book' is the first definition.
(I've seen this before)
'plant' is the second definition.
(annual is a type of plant)
(Other definitions for annual that I've seen before include "Book published yearly" , "Lasting for a year" , "Plant; yearbook" , "Reference book that's published every year" , "Type of year book" .)