Even-tempered, just having dropped it (7)
I believe the answer is:
equable
'even-tempered' is the definition.
('equable' can be a synonym of 'even-tempered')
'just having dropped it' is the wordplay.
'just' becomes 'equitable' ('equitable' can be a synonym of 'just').
'having dropped' suggests deleting specific letters.
'equitable' with 'it' removed is 'EQUABLE'.
(Other definitions for equable that I've seen before include "not easily rattled" , "Good-natured" , "Not extreme" , "Not easily angered" , "Calm, even-tempered" .)