Faint moody expression about a case of shingles (4,3)
I believe the answer is:
pass out
'faint' is the definition.
('pass out' can be a synonym of 'faint')
'moody expression about a case of shingles' is the wordplay.
'moody expression' becomes 'pout'.
'about' is an insertion indicator.
'case of' suggests removing the centre (outsides of).
'shingles' with its middle taken out is 'ss'.
'a'+'ss'='ass'
'pout' enclosing 'ass' is 'PASS-OUT'.
(Other definitions for pass out that I've seen before include "Complete one's training" , "Lose consciousness" , "Graduate - faint" , "In the army, do so having proved ready" , "drop" .)