Record find? Not half! (4)
I believe the answer is:
disc
'record' is the definition.
(eg a CD, compact disc)
'find? not half' is the wordplay.
'find?' becomes 'discover' ('discover' can be a synonym of 'find').
'not half' indicates taking half.
'discover' cut in half is 'DISC'.
(Other definitions for disc that I've seen before include "One of 33, 45 or 78?" , "45, eg?" , "Protein-constituent acid" , "Layer of cartilege between vertebrae" , "Capital of India" .)