Unwell after cold hotel — could be this (5)
I believe the answer is:
chill
'be this' is the definition.
The definition suggests a singular noun which matches the answer.
'unwell after cold hotel' is the wordplay.
'unwell' becomes 'i'll' (similar in meaning).
'after' is a charade indicator (letters next to each other).
'cold' becomes 'C' (eg on taps).
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'c'+'h'='ch'
'ill' after 'ch' is 'CHILL'.
'could' acts as a link.
Can you help me to learn more?
(Other definitions for chill that I've seen before include "Feverish cold; relax" , "Slight cold" , "Make cold (or frightened)" , "Slang injunction to relax - it's cold" , "Make cool" .)