A principal's further on (5)

I believe the answer is:

ahead

'further on' is the definition.
(I've seen this before)

'a principal's' is the wordplay.
'principal' becomes 'head' (synonyms).
'a'+'head'='AHEAD'

(Other definitions for ahead that I've seen before include "In the lead, in advance" , "in van" , "In the vanguard" , "likely to win?" , "In front as in race" .)

I've seen this clue in The Telegraph.

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