Argument involving knight in decayed building (3-2)
I believe the answer is:
run-in
'argument' is the definition.
(I've seen this before)
'knight in decayed building' is the wordplay.
'knight' becomes 'N' (chess abbreviation).
'in' indicates putting letters inside.
'decayed building' becomes 'ruin' (ruin is a kind of building. I am not sure about the 'decayed' bit.).
'n' going into 'ruin' is 'RUN-IN'.
'involving' is the link.
Can you help me to learn more?
(Other definitions for run-in that I've seen before include "Quarrel" , "Dispute" , "Approach" , "Matches late in season" , "Fight, disagreement" .)
