Fast mover covering return of service that's very delicate (8)
I believe the answer is:
gossamer
'very delicate' is the definition.
'gossamer' can be an answer for 'delicate' (similar in meaning). I am not certain of the 'very' bit.
'fast mover covering return of service' is the wordplay.
'fast mover' becomes 'goer' (I can't justify this - if you can you should believe this answer much more).
'covering' means one lot of letters goes inside another.
'return of' says the letters should be written backwards.
'service' becomes 'mass' (kind of church service).
'mass' reversed gives 'ssam'.
'goer' enclosing 'ssam' is 'GOSSAMER'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for gossamer that I've seen before include "fine material" , "Fine spider's silk" , "very flimsy stuff" , "Very thin material" , "Spider silk" .)