After work note mother is best (7)
I believe the answer is:
optimum
'is best' is the definition.
(optimum means the best possible)
'after work note mother' is the wordplay.
'after' is a charade indicator (letters next to each other).
'work' becomes 'op' (abbreviation for opus).
'note' becomes 'ti' (musical note, as in do re mi so fa la ti do).
'mother' becomes 'mum' (informal term for mother).
'op' next to 'ti' is 'opti'.
'opti'+'mum'='OPTIMUM'
(Other definitions for optimum that I've seen before include "Most favourable amount" , "Most favourable point" , "model" , "top condition" , "Best (result)" .)