Machine of material interest (4)
I believe the answer is:
loom
'machine' is the definition.
(loom is a kind of machine)
'of material interest' is the wordplay.
I cannot quite see how this works, but
'of' could be 'o' and 'o' is found in the answer.
The remaining letters 'lom' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for loom that I've seen before include "Apparatus for weaving cloth" , "Apparatus for weaving yarn" , "'Appear as a vague form, perhaps threatening (4)'" , "tower" , "Rise up threateningly ahead" .)