Ruddy prickly aid organisation (3,5)
I believe the answer is:
red cross
'organisation' is the definition.
(Red Cross is an example)
'ruddy prickly aid' is the wordplay.
'ruddy' becomes 'red' (synonyms).
'prickly aid' becomes 'cross' (I can't justify this - if you can you should give a lot more credence to this answer).
'red'+'cross'='RED-CROSS'
Can you help me to learn more?
(Other definitions for red cross that I've seen before include "International organisation for care of wounded in war" , "International organisation for helping war-wounded" , "International oranisation for treatment of wounded in war" , "Humanitarian outfit" , "International humanitarian organization" .)