The master went out and caught, again, a bad cold (8)
I believe the answer is:
streamer
'a bad cold' is the definition.
'streamer' can be an answer for 'cold' (I've seen this before). I am not certain of the 'a bad' bit.
'the master went out and caught again' is the wordplay.
'went out' indicates anagramming the letters (I've seen 'goes out' mean this).
'and' is a charade indicator (letters next to each other).
'caught again' becomes 'er' (I can't explain this - if you can you should give a lot more credence to this answer).
'master' anagrammed gives 'stream'.
'stream'+'er'='STREAMER'
Can you help me to learn more?
(Other definitions for streamer that I've seen before include "shocking cold?" , "Long narrow ribbon for er, master" , "terrible cold?" , "Banner, flag; fishing fly" , "Paper ribbon - thin flag" .)