Powerful result I have (9)
I believe the answer is:
effective
'powerful' is the definition.
(I've seen this before)
'result i have' is the wordplay.
'result' becomes 'effect' ('effect' can be a synonym of 'result'**).
'i have' becomes 'ive'.
'effect'+'ive'='EFFECTIVE'
(Other definitions for effective that I've seen before include "Powerful" , "Accomplishing an objective, efficient" , "Practical or operative" , "operative > producing the desired result" , "In operation" .)