Lift firm books onto one shelf at the top (4)
I believe the answer is:
otis
'lift firm' is the definition.
(Otis is an elevator company)
'books onto one shelf at the top' is the wordplay.
'books' becomes 'OT' (abbreviation for Old Testament).
'onto' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'at the top' indicates taking the first letters.
The initial letter of 'shelf' is 's'.
'ot'+'i'+'s'='OTIS'
(Other definitions for otis that I've seen before include "Cole Porter's miss who was "unable to lunch today"" , "- - Redding (soul music star)" , "Miss -- Regrets, Cole Porter song" , "Company providing lifts" , "Place of worship; side part of head" .)