Mending one hospital garment is an ordeal (9)
I believe the answer is:
nightmare
'an ordeal' is the definition.
(thesaurus)
'mending one hospital garment' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'hospital' could be 'h' and 'h' is found within the answer.
an anagram of 'garment' is 'ngtmare' which is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'is' is the link.
Can you help me to learn more?
(Other definitions for nightmare that I've seen before include "causing distress to the Lord Chancellor?" , "Horrifying experience" , "Bad dream" , "Awful experience" , "dreadful experience" .)