Mother's ready to receive energy from particle (2-5)
I believe the answer is:
'particle' is the definition.
(mu-meson is a kind of particle)
'mother's ready to receive energy' is the wordplay.
'mother's' becomes 'mums' (mum is a kind of mother).
'ready' becomes 'on' (if a device is on it is ready for use).
'to receive' means one lot of letters goes inside another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'mumson' placed around 'e' is 'MU-MESON'.
'from' acts as a link.