Tiny matter? (4)
I believe the answer is:
atom
'tiny matter?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for atom that I've seen before include "Moat (anag.)" , "A mighty particle, makes huge explosion" , "Minute fragment" , "Smallest particle in an element able to take part in a chemical reaction" , "A tiny particle of matter with a big bang" .)