Mum's dumping Mike for somebody else (5)
I believe the answer is:
other
'else' is the definition.
(similar in meaning)
'mum's dumping mike' is the wordplay.
'mum' becomes 'mother' (I've seen this before).
'dumping' is a deletion indicator.
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'mother' with 'm' taken out is 'OTHER'.
'for somebody' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for other that I've seen before include "Distinct" , "Remaining" , "Different, disparate" , "Second" , "Different, alternative" .)