Declare love and, primarily, respect for a teacher (9)
I believe the answer is:
professor
'a teacher' is the definition.
(thesaurus)
'declare love and primarily respect' is the wordplay.
'declare' becomes 'profess' (professing is a kind of declaring**).
'love' becomes 'o' (In tennis, 'love' means 'zero').
'and' says to put letters next to each other.
'primarily' suggests taking the first letters.
The initial letter of 'respect' is 'r'.
'profess'+'o'+'r'='PROFESSOR'
'for' is the link.
(Other definitions for professor that I've seen before include "Member of an academic faculty" , "One affirming faith" , "Leading academic" , "One who claims" , "Top university teacher" .)