Flatulence firstly hazardous being full of beans (6)
I believe the answer is:
frisky
'full of beans' is the definition.
(thesaurus)
'flatulence firstly hazardous' is the wordplay.
'firstly' indicates taking the first letters.
'hazardous' becomes 'risky' (synonyms).
The first letter of 'flatulence' is 'f'.
'f'+'risky'='FRISKY'
'being' is the link.
(Other definitions for frisky that I've seen before include "In high spirits" , "Energetically playful" , "Lively like playful dog" , "Playful, full of energy" , "Frolicsome" .)