I love and I appreciate that Greek character (4)
I believe the answer is:
iota
'greek character' is the definition.
(letter from the Greek alphabet)
'i love and i appreciate that' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'and' means one lot of letters go next to another.
'i appreciate that' becomes 'ta' (informal way of saying thank you).
'i'+'o'+'ta'='IOTA'
(Other definitions for iota that I've seen before include "Trace" , "letter from abroad" , "letter from Greece" , "Smidgeon" , "Ninth letter of Greek alphabet, small amount" .)