Fastidious Everyman given time: 'silly not to deliver' (10)
I believe the answer is:
meticulous
'fastidious' is the definition.
(similar in meaning)
'everyman given time silly not to deliver' is the wordplay.
I cannot really understand how this works, but
'everyman' could be 'me' (where 'Everyman' is the setter of the crossword) and 'me' is present in the answer.
'time' could be 't' (abbreviation) and 't' is located in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for meticulous that I've seen before include "Extremely careful" , "of great precision" .)