Guy and Bill post a student yearbook (7)
I believe the answer is:
almanac
'yearbook' is the definition.
(I know that almanac is a type of yearbook)
'guy and bill post a student' is the wordplay.
'guy' becomes 'man' (guy can informally mean a man).
'and' is a charade indicator (letters next to each other).
'bill' becomes 'ac' (short for account).
'post' says to put letters next to each other (post- can mean after).
'student' becomes 'l' (as in L-plates for learner drivers).
'man'+'ac' is 'manac'.
'a'+'l'='al'
'manac' put after 'al' is 'ALMANAC'.
(Other definitions for almanac that I've seen before include "periodic publication" , "Calendar with detailed information" , "Annual publication containing information in a particular field" , "Statistical calendar" , "Annual reference book" .)