Caught shy fish (3)
I believe the answer is:
koi
'fish' is the definition.
(koi is a type of fish)
'caught shy' is the wordplay.
'caught' shows a homophone (sound like) (to catch something can mean to hear it).
'shy' becomes 'coy' (coy can mean shy or modest).
'coy' sounds like 'KOI'.
(Other definitions for koi that I've seen before include "Japanese fish" , "Large Japanese carp" , "Ornamental carp variety" , "Colourful ornamental carp" , "Carp; sounds like shy" .)