Play part killing Romeo in a dazed state (9)
I believe the answer is:
tolerance
'play' is the definition.
(both can mean room for movement in engineering)
'part killing romeo in a dazed state' is the wordplay.
'part killing romeo' becomes 'ole' (I am not sure about this - if you are sure you should believe this answer much more).
'in' is an insertion indicator.
'a dazed state' becomes 'trance' (I've seen this in another clue).
'ole' going into 'trance' is 'TOLERANCE'.
Can you help me to learn more?
(Other definitions for tolerance that I've seen before include "Ability to resist pain" , "Allowable variation (in a dimension)" , "resignation" , "Understanding" , "Amount of play" .)