A spring flourish (6)
I believe the answer is:
abound
'flourish' is the definition.
(I've seen this before)
'a spring' is the wordplay.
'spring' becomes 'bound' (bounding is a kind of springing).
'a'+'bound'='ABOUND'
(Other definitions for abound that I've seen before include "rich" , "Be widely available" , "Be plentiful, swarm" , "On a bud (anag)" , "flow" .)