Quarrel in royal marriage, without love... (3-2)
I believe the answer is:
run-in
'quarrel' is the definition.
(I've seen this before)
'in royal marriage without love' is the wordplay.
'in royal' becomes 'r' (abbreviation. I am not sure about the 'in' bit.).
'marriage' becomes 'union' (synonyms).
'without' indicates named letters should be taken away.
'love' becomes 'o' (love means zero in tennis).
'union' with 'o' taken away is 'unin'.
'r'+'unin'='RUN-IN'
Can you help me to learn more?
(Other definitions for run-in that I've seen before include "Matches late in season" , "Fight, disagreement" , "Approach" , "Dispute" , "Home straight" .)