Gert's upset about getting a bit wet when there's hail! (5)
I believe the answer is:
greet
'hail' is the definition.
(I know that greet is a is a more specific form of the action of hail)
'gert's upset about getting a bit' is the wordplay.
'upset' indicates anagramming the letters.
'about' indicates putting letters inside.
'getting a bit' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'gert' anagrammed gives 'gret'.
'gret' placed around 'e' is 'GREET'.
'wet when there's' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for greet that I've seen before include "Address on arrival, say hello" , "Meet and salute" , "Give welcome to" , "Make welcome" , "Acknowledge" .)