Disappear without queen overcome (8)
I believe the answer is:
vanquish
'overcome' is the definition.
(I've seen this before)
'disappear without queen' is the wordplay.
'disappear' becomes 'vanish' ('vanish' can be a synonym of 'disappear').
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'queen' becomes 'qu'.
'vanish' enclosing 'qu' is 'VANQUISH'.
(Other definitions for vanquish that I've seen before include "Defeat in a contest" , "Defeat in battle" , "Defeat, conquer" , "Best" , "Defeat, overcome someone" .)