Show poor average (4)
I believe the answer is:
mean
I believe this is a triple definition!
'show' is the first definition.
(I've seen this before)
'poor' is the second definition.
(similar in meaning)
'average' is the third definition.
(type of average)
(Other definitions for mean that I've seen before include "mercenary" , "Signify; tight" , "Close" , "intimate" , "Parsimonious" .)