G-man about, always excited (7)
I believe the answer is:
fevered
'excited' is the definition.
(similar in meaning)
'g-man about always' is the wordplay.
'g-man' becomes 'fed' (I've seen this in another clue).
'about' indicates putting letters inside.
'always' becomes 'ever' (synonyms).
'fed' going around 'ever' is 'FEVERED'.
(Other definitions for fevered that I've seen before include "Impatient" , "Nervously excited" , "Highly excited" .)