Mental conception of one poor game (5)
I believe the answer is:
image
'mental conception' is the definition.
'image' can be an answer for 'conception' (I've seen this in another clue). I am unsure of the 'mental' bit.
'one poor game' is the wordplay.
'one' becomes 'i' (Roman numeral).
'poor' indicates an anagram.
'game' is an anagram of 'mage'.
'i'+'mage'='IMAGE'
'of' is the link.
Can you help me to learn more?
(Other definitions for image that I've seen before include "Optical counterpart in mirror" , "Pictorial representation" , "Likeness U symbol" , "Picture (involving one letter change from 10)" , "Likeness or mental picture" .)