Just a little short of quality (4)
I believe the answer is:
fair
'just' is the definition.
(just can mean fair in the sense of showing justice)
'a little short of quality' is the wordplay.
'a little short of' becomes 'f' (I can't justify this - if you can you should believe this answer much more).
'quality' becomes 'air' (air is a kind of quality).
'f'+'air'='FAIR'
Can you help me to learn more?
(Other definitions for fair that I've seen before include "Impartial, so-so" , "(Of weather) fine and dry" , "Traders' gathering" , "likely" , "Attractive type of weather?" .)