Apprehensive over Sun getting involved! (7)
I believe the answer is:
nervous
'apprehensive' is the definition.
('nervous' can be a synonym of 'apprehensive')
'over sun getting involved' is the wordplay.
'getting involved' indicates anagramming the letters.
'over'+'sun'='oversun'
'oversun' anagrammed gives 'NERVOUS'.
(Other definitions for nervous that I've seen before include "stewing" , "Feeling or showing anxiety" , "Jittery" , "Agitated and apprehensive" , "Jumpy" .)