Horrid stay got worse after midday (5)
I believe the answer is:
nasty
'horrid' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nasty that I've seen before include "One who sees the future" , "Highly unpleasant" , "Spiteful and unkind" , "Foul" , "Obscene" .)