In front of a principal (5)
I believe the answer is:
ahead
'in front of' is the definition.
(I've seen this in another clue)
'a principal' 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" , "Forward - in front" , "In the future" , "advanced" , "In the leading position" .)