Conceal son alongside mum (7)
I believe the answer is:
smother
'conceal' is the definition.
(I've seen this before)
'son alongside mum' is the wordplay.
'son' becomes 's'.
'alongside' is a charade indicator (letters next to each other).
'mum' becomes 'mother' (I've seen this before).
's'+'mother'='SMOTHER'
(Other definitions for smother that I've seen before include "Kill by depriving of air" , "Suffocate, stifle" , "Extinguish (fire) by covering it" , "Put out" , "Muffle" .)