Less than adequate discount, perhaps (6-4)
I believe the answer is:
second-rate
'less' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'adequate discount perhaps' is the wordplay.
'adequate' becomes 'second' (I can't justify this - if you can you should believe this answer much more).
'discount perhaps' becomes 'rate' (discount is a kind of rate).
'second'+'rate'='SECOND-RATE'
'than' acts as a link.
Can you help me to learn more?
(Other definitions for second-rate that I've seen before include "Poor" , "Of mediocre quality" , "Inferior" , "Shoddy" , "Substandard" .)