Lay hands on book of not so great size (5)
I believe the answer is:
bless
'lay hands on' is the definition.
(thesaurus)
'book of not so great size' is the wordplay.
'book' becomes 'b' (abbreviation for book).
'of not so great size' becomes 'less' (less prominent or big).
'b'+'less'='BLESS'
(Other definitions for bless that I've seen before include "Wish happiness" , "Call on God to favour" , "Give benediction" , "Isn't that sweet?" , "Consecrate; be thankful for" .)