Noise made by an owl or a duck when it's warm outside (4)
I believe the answer is:
hoot
'noise made by an owl or a' is the definition.
I can't tell whether this definition defines the answer.
'duck when it's warm outside' is the wordplay.
'duck when' becomes 'o' (resembles zero - 'duck' in cricket. I am not sure about the 'when' bit.).
'it's warm' becomes 'hot' (associated in meaning).
'outside' means one lot of letters goes inside another (some letters go outside others).
'o' put into 'hot' is 'HOOT'.
Can you help me to learn more?
(Other definitions for hoot that I've seen before include "Funny thing (informal);bird call" , "Owl's sound" , "Owlish cry" , "Hollow cry" , "Cry of owl" .)