Unruffled by lifting of some hygiene restrictions (6)
I believe the answer is:
serene
'unruffled' is the definition.
(thesaurus)
'lifting of some hygiene restrictions' is the wordplay.
'lifting of' says the letters should be written in reverse.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'eneres' is hidden in the letters of 'hygiene restrictions'.
'eneres' written backwards gives 'SERENE'.
'by' is the link.
(Other definitions for serene that I've seen before include "Peaceful and contented" , "Tranquil, unruffled" , "Calm and at peace" , "without any trouble" , "Calm, peaceful, tranquil" .)