Harry sent thrones, creating very unpleasant situation (7,4)
I believe the answer is:
hornets nest
'very unpleasant situation' is the definition.
'hornets nest' can be an answer for 'situation' (I have seen 'hazardous situation' mean 'hornets nest' so perhaps 'situation' could also mean 'hornets nest'). I am unsure of the 'very unpleasant' bit.
'harry sent thrones' is the wordplay.
'harry' is an anagram indicator (harry can mean to attack or spoil).
'sent'+'thrones'='sentthrones'
'sentthrones' anagrammed gives 'HORNETS NEST'.
'creating' acts as a link.
Can you help me to learn more?
(Other definitions for hornets nest that I've seen before include "Something not to be stirred up" , "Big trouble!" , "Stirred up it's dangerous" , "(Stir up a) violent reaction" , "hazardous situation" .)