Reserve Grant a little reading (7)
I believe the answer is:
booklet
'a little reading' is the definition.
(small book)
'reserve grant' is the wordplay.
'reserve' becomes 'book' (to book something is to reserve it).
'grant' becomes 'let' (I've seen this in another clue).
'book'+'let'='BOOKLET'
(Other definitions for booklet that I've seen before include "Small tome" , "Small manual" , "Brochure" , "Small publication" , "Thin publication" .)