Concerned with small emergency arising once more (9)
I believe the answer is:
resurgent
'arising once more' is the definition.
(surging or arising again)
'concerned with small emergency' is the wordplay.
'concerned with' becomes 're' (re can mean regarding, concerning).
'small' becomes 's' (abbreviation - e.g. clothes size).
'emergency' becomes 'urgent'.
're'+'s'+'urgent'='RESURGENT'
(Other definitions for resurgent that I've seen before include "Reviving after period of inactivity" , "Reviving after a lull" , "Coming back to life" , "reborn" , "Reviving in popularity" .)