Likely corrupt lab is covered by investigation (8)
I believe the answer is:
probable
'likely' is the definition.
('probable' can be a synonym of 'likely')
'corrupt lab is covered by investigation' is the wordplay.
'corrupt' indicates an anagram.
'is covered by' indicates putting letters inside.
'investigation' becomes 'probe' ('probe' can be a synonym of 'investigation'**).
'lab' is an anagram of 'abl'.
'abl' placed within 'probe' is 'PROBABLE'.
(Other definitions for probable that I've seen before include "on the cards" , "Likely to be the case" , "Person most likely" , "Like to happen" , "Seeming to have a good chance of happening" .)