Avail oneself of totally in a way that's helpful (8)

I believe the answer is:

usefully

'in a way that's helpful' is the definition.

'avail oneself of totally' is the wordplay.
'avail oneself of' becomes 'use' (I've seen this before).
'totally' becomes 'fully'.
'use'+'fully'='USEFULLY'

(Other definitions for usefully that I've seen before include "Advantageously" , "To produce a benefit" , "in an advantageous way" , "in a way that's beneficial" , "In a productive manner" .)

I've seen this clue in the Evening Standard.

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