Human cell impeded by introduction of tritium particle (7)
I believe the answer is:
neutron
'particle' is the definition.
(type of sub-atomic particle)
'human cell impeded by introduction of tritium' is the wordplay.
I cannot really see how this works, but
'cell' could be 't' (T cell is an example) and 't' is found within the answer.
'of' could be 'o' and 'o' is found within the answer.
'human' could be 'rn' (RN is an example) and 'rn' is located in the leftover letters.
The remaining letters 'neu' 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 neutron that I've seen before include "Charged particle" , "Turn one (anag) - kind of bomb" , "Particle that decays when released" , "On tuner (anag.)" , "one's not charged" .)