Shy and put out when red spots appear (6)
I believe the answer is:
typhus
'red spots appear' is the definition.
I can't judge whether this defines the answer.
'shy and put out' is the wordplay.
'and' says to put letters next to each other.
'out' indicates an anagram (out can mean wrong or inaccurate).
'shy' after 'put' is 'putshy'.
'putshy' is an anagram of 'TYPHUS'.
'when' is the link.
Can you help me to learn more?
(Other definitions for typhus that I've seen before include "Disease found in spy hut, strangely" , "Infectious disease transmitted by lice" , "Acute, infectious fever" , "Disease causing high fever and skin rash" , "Dangerous fever transmitted by lice" .)