One acted in poor show (8)
I believe the answer is:
indicate
'show' is the definition.
(I know that show can be written as indicate)
'one acted in poor' is the wordplay.
'one' becomes 'i' (Roman numeral).
'poor' indicates an anagram.
'acted'+'in'='actedin'
'actedin' is an anagram of 'ndicate'.
'i'+'ndicate'='INDICATE'
(Other definitions for indicate that I've seen before include "Make a signal" , "Point, show, signal" , "Mark" , "(Give a) signal" , "Point out or give some notion of" .)