Cheap reserved boxes out of left-field (6)
I believe the answer is:
shoddy
'cheap' is the definition.
(I've seen this in another clue)
'reserved boxes out of left-field' is the wordplay.
'reserved' becomes 'shy' (I've seen this before).
'boxes' means one lot of letters goes inside another (the outside letters must 'box' inside letters in).
'out of left field' becomes 'odd' (I can't justify this - if you can you should give a lot more credence to this answer).
'shy' enclosing 'odd' is 'SHODDY'.
Can you help me to learn more?
(Other definitions for shoddy that I've seen before include "Cheap and poorly made" , "Gimcrack" , "bits of waste material" , "Kind of worsted" , "inferior cloth" .)