Child upset by rain on its bare head (5)
I believe the answer is:
bairn
'child' is the definition.
(Scottish and northern English term for a child)
'upset by rain on its bare head' is the wordplay.
I cannot really see how this works, but
an anagram of 'rain' is 'airn' which is within the answer.
A single letter 'b' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bairn that I've seen before include "A tot of Scotch" , "little one in Yorkshire" , "A Scottish child?" , "Child in Scotland" , "Scots child" .)