Fix page on the French book (5)
I believe the answer is:
plant
'fix' is the definition.
(I know that fix is a more specific form of plant)
'page on the french book' is the wordplay.
'page' becomes 'p'.
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'the french' becomes 'la' (one of the French words for 'the').
'book' becomes 'nt' (New Testament).
'p'+'la'+'nt'='PLANT'
(Other definitions for plant that I've seen before include "One placed in a group as an informer" , "sold by garden centre" , "Shrub - factory" , "that goes to pot" , "Vegetable organism" .)