Appeal of polytechnic's first principal (5)
I believe the answer is:
plead
'appeal' is the definition.
(pleading is a kind of appealing)
'polytechnic's first principal' is the wordplay.
'first' suggests taking the first letters.
'principal' becomes 'lead' ('lead' can be a synonym of 'principal'**).
The first letter of 'polytechnic' is 'p'.
'p'+'lead'='PLEAD'
'of' is the link.
(Other definitions for plead that I've seen before include "Sue" , "Argue (a position in court)" , "Implore, entreat" , "Present an argument in court" , "Argue (for a cause)" .)