Fail to show fish? (4)
I believe the answer is:
pike
'fish?' is the definition.
(pike is a kind of fish)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for pike that I've seen before include "Voracious freshwater fish" , "dive in this position" , "Fish; weapon; hill" , "Position of one diving" , "Imitating earlier style" .)