Frightened fish caught by the Poles (6)
I believe the answer is:
shaken
'frightened' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?
'fish caught by the poles' is the wordplay.
'fish' becomes 'hake' (type of fish).
'caught by' is an insertion indicator.
'the poles' becomes 'sn' (North and South poles).
'hake' put inside 'sn' is 'SHAKEN'.
Can you help me to learn more?
(Other definitions for shaken that I've seen before include "Distressed" , "jarred" , "Shocked; brandished" , "Upset or agitated" , "Upset - rattled" .)