Boy, caught by stream, a source of irritation (7)
I believe the answer is:
sunburn
'a source of irritation' is the definition.
I can't tell whether this defines the answer.
'boy caught by stream' is the wordplay.
'boy' becomes 'son' (synonyms).
'caught' shows a homophone (sound like) (to catch something can mean to hear it).
'by stream' becomes 'burn' (a burn is a small stream. I am not sure about the 'by' bit.).
'son' sounds like 'sun'.
'sun'+'burn'='SUNBURN'
Can you help me to learn more?
(Other definitions for sunburn that I've seen before include "Effect of too much UV" , "Redness of the skin caused by solar rays" , "Reddening of skin" , "Overexposure to UV" , "Solar skin damage" .)