Shows fear when henhouse door is left open! (8,3)
I believe the answer is:
chickens out
'shows fear when henhouse door' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'left open' is the wordplay.
'left' becomes 'chickens' (I can't explain this - if you can you should give a lot more credence to this answer).
'open' becomes 'out' (I've seen this in other clues).
'chickens'+'out'='CHICKENS OUT'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for chickens out that I've seen before include "emergency at the poultry farm?" , "Behaves like a coward" .)