It was less than fortunate, being caught (4)
I believe the answer is:
tuna
'it was less' is the definition.
The definition suggests a singular noun which matches the answer.
'than fortunate being caught' is the wordplay.
'being caught' says the answer is hidden in the clue (I've seen 'catches' mean this (the answer is caught in the clue)).
'TUNA' can be found hidden inside 'than fortunate'.
Can you help me to learn more?
(Other definitions for tuna that I've seen before include "Large sea-fish" , "Marine food fish" , "Tinned food fish" , "Warm-water food fish" , "Bluefin, e.g." .)