Virtually nothing collected by charity that's closing (6)
I believe the answer is:
almost
'virtually' is the definition.
(synonyms)
'nothing collected by charity that's closing' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'collected by' is an insertion indicator.
'charity' becomes 'alms' (alms is a kind of charity).
'closing' suggests the final letters (the letter which ends or closes the word).
The final letter of 'that' is 't'.
'o' inserted inside 'alms' is 'almos'.
'almos'+'t'='ALMOST'
(Other definitions for almost that I've seen before include "practically" , "Slightly short of" , "As good as" , "Not totally" , "Well-nigh" .)