Bemoan missing New Testament material (4)
I believe the answer is:
lame
'material' is the definition.
(I know that lame is a type of material)
'bemoan missing new testament' is the wordplay.
'bemoan' becomes 'lament' (synonyms).
'missing' is a deletion indicator.
'new testament' becomes 'nt'.
'lament' with 'nt' taken out is 'LAME'.
(Other definitions for lame that I've seen before include "Halting or unconvincing like poor excuse" , "Fabric interwoven with metal threads" , "Weak and unconvincing like injured foot" , "Thin plate" , "Walking with a limp" .)