Trimming faulty tile with NHS emblem (13)
I believe the answer is:
embellishment
'trimming' is the definition.
(thesaurus)
'faulty tile with nhs emblem' is the wordplay.
'faulty' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'tile'+'nhs'+'emblem'='tilenhsemblem'
'tilenhsemblem' with letters rearranged gives 'EMBELLISHMENT'.
(Other definitions for embellishment that I've seen before include "Fictitious addition" , "Detail, often untrue, added to a story to make it more interesting" , "Adornment, decoration" , "Elaboration" , "Additional beautification" .)