Strong, pure flow in circulation (8)
I believe the answer is:
powerful
'strong' is the definition.
('powerful' can be similar in meaning to 'strong')
'pure flow in circulation' is the wordplay.
'in circulation' indicates anagramming the letters.
'pure'+'flow'='pureflow'
'pureflow' anagrammed gives 'POWERFUL'.
(Other definitions for powerful that I've seen before include "Dominant" , "Potent, forceful" , "Pure wolf (anag.)" , "Having a strong effect" , "Like a potentate" .)