Choose one for mother - the best! (7)

I believe the answer is:

optimum

'the best' is the definition.
(optimum means the best possible)

'choose one for mother' is the wordplay.
'choose' becomes 'opt' (both can mean to pick something).
'one' becomes 'i' (Roman numeral).
'for' means one lot of letters go next to another.
'mother' becomes 'mum' (informal term for mother).
'opt'+'i'+'mum'='OPTIMUM'

(Other definitions for optimum that I've seen before include "Most appropriate" , "Most favourable point" , "model" , "The best possible" , "Most favourable (conditions)" .)

I've seen this clue in the Evening Standard.

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