Checked what monarch did, abandoning grand home (6,2)
I believe the answer is:
reined in
'checked' is the definition.
(I've seen this before)
'what monarch did abandoning grand home' is the wordplay.
'what monarch did' becomes 'reigned'.
'abandoning' suggests deleting specific letters.
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'home' becomes 'in' ('he's home' can mean 'he's in').
'reigned' with 'g' removed is 'reined'.
'reined'+'in'='REINED IN'
(Other definitions for reined in that I've seen before include "Stopped or slowed up, a horse perhaps" , "Slowed up one's horse" , "Checked - stopped" , "restricted" , "Curbed" .)