Excuse a page on science (7)
I believe the answer is:
apology
'excuse' is the definition.
(I know that excuse can be written as apology)
'a page on science' is the wordplay.
'page' becomes 'p'.
'on' is a charade indicator (letters next to each other).
'science' becomes 'ology' (I've seen this before).
'a'+'p'+'ology'='APOLOGY'
(Other definitions for apology that I've seen before include "Confession" , "Poor substitute" , "A poor example" , "Acknowledgment of an offence" , "Saying sorry; poor specimen" .)