Extremely happy being in charge, likely to boom? (10)
I believe the answer is:
hypersonic
'likely to boom?' is the definition.
(I've seen this before)
'extremely happy being in charge' is the wordplay.
'extremely' suggests removing the centre.
'being' becomes 'person' (person is a kind of being**).
'in charge' becomes 'ic'.
'happy' with its middle removed is 'hy'.
'hy'+'person'+'ic'='HYPERSONIC'
(Other definitions for hypersonic that I've seen before include "Faster than Mach 5" , "likely to boom" , "lightning quick?" , "very fast" , "Very much faster than sound" .)