Revealing some material in Times earlier now and then (8)
I believe the answer is:
telltale
'revealing' is the definition.
(I know that revealing can be written as telltale)
'some material in times earlier now and then' is the wordplay.
'some material' becomes 'ell' (ell is a historical measurement of cloth).
'in' indicates putting letters inside.
'times' becomes 'tt' (two abbreviations for time).
'now and then' indicates alternate letters (letters taken on a regular basis, now and then).
The alternating letters of 'earlier' are 'ale'.
'ell' inserted within 'tt' is 'tellt'.
'tellt'+'ale'='TELLTALE'
(Other definitions for telltale that I've seen before include "Informer - monitoring device" , "Gossip-monger" , "Blabbing person" , "private reporter" , "Blabbermouth, snitch" .)