Pack strikingly well (4)
I believe the answer is:
tamp
This could be a double definition.
'pack' is the first definition.
('tamp' can be a synonym of 'pack')
'strikingly well' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
Can you help me to learn more?
(Other definitions for tamp that I've seen before include "Pack down eg tobacco in a pipe" , "Compact" , "Press, pack (down)" , "Push down tobacco" , "press down firmly" .)