Relieved the head cold had come to an end (6)
I believe the answer is:
ceased
'end' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can sometimes define each other.
'relieved the head cold had come to an' is the wordplay.
I cannot quite see how this works, but
'relieved' could be 'eased' (easing is a kind of relieving) and 'eased' is present in the answer.
'cold' could be 'c' (eg on taps) and 'c' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ceased that I've seen before include "Stopped, quitted" , "Concluded" , "Stopped, ended" , "Stopped, desisted" , "Finished" .)