Undiminished (8)
I believe the answer is:
unabated
'undiminished' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for unabated that I've seen before include "Not calmed or diminished, say storm" , "Without diminution" , "not weakening" , "with no loss of intensity" , "without loss of power" .)