Cram for an examination (5)
I believe the answer is:
study
This clue is a double definition.
'cram' is the first definition.
(thesaurus)
'an examination' is the second definition.
(study is a kind of examination)
'for' is the link.
(Other definitions for study that I've seen before include "Room for work/reading" , "Learn; den" , "Investigate" , "Read up - academic work" , "Read to learn" .)