This country is back — after having an illness — that's just for starters (5)
I believe the answer is:
haiku
'this' is the definition.
The definition suggests a singular noun which matches the answer.
'country is back after having an illness that's just for starters' is the wordplay.
'country' becomes 'uk' (United Kingdom).
'is back' says the letters should be written in reverse.
'after' is a charade indicator (letters next to each other).
'that's just for starters' says to take the initial letters.
The initial letters of 'having an illness' is 'hai'.
'uk' in reverse letter order is 'ku'.
'ku' after 'hai' is 'HAIKU'.
Can you help me to learn more?
(Other definitions for haiku that I've seen before include "Jap 17 syllable poem" , "Short Japanese poem" , "Japanese poem of seventeen syllables comprising three lines" , "Pithy lines" , "Japanese form of poem" .)