Brief illness - flu perhaps? (11)
I believe the answer is:
'flu perhaps?' is the definition.
I can't judge whether this defines the answer.
'brief illness' is the wordplay.
'brief' becomes 'curt' (synonyms).
'illness' becomes 'ailment' (an ailment is an illness or health problem).
Can you help me to learn more?
(Other definitions for curtailment that I've seen before include "Contraction" , "Terminal cut (anag) - downsizing" , "premature end" , "Abridgement, shortening" , "Bringing to an end" .)