Frolic before friend with a gloomy air (10)
I believe the answer is:
funereally
'with a gloomy air' is the definition.
(befitting a funeral)
'frolic before friend' is the wordplay.
'frolic' becomes 'fun' (a frolic can mean some fun).
'before' becomes 'ere' (poetic term for 'before').
'friend' becomes 'ally' (an ally is a friend or supporter).
'fun'+'ere'+'ally'='FUNEREALLY'
(Other definitions for funereally that I've seen before include "dismally" , "Lacking joy" .)