Short measure after love letter from Greece (7)
I believe the answer is:
omicron
'letter from greece' is the definition.
(letter from the Greek alphabet)
'short measure after love' is the wordplay.
'short measure' becomes 'micron' (micron is a kind of measure. I am not sure about the 'short' bit.).
'after' means one lot of letters go next to another.
'love' becomes 'o' (love means zero in tennis).
'micron' after 'o' is 'OMICRON'.
Can you help me to learn more?
(Other definitions for omicron that I've seen before include "Greek short 'o'" , "Foreign letter -- I'm no roc (anag)" , "A rounded character" , "Greek character" , "Olympic character" .)