Covertly (8)
'covertly' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for secretly that I've seen before include "Covertly" , "On the q.t" , "under cover" , "behind closed doors" , "without telling anyone" .)
(Another definition for insecret that I've seen is " Concealed".)
(Other definitions for surreptitiously that I've seen before include "not 14 [OVERTLY]" , "in secret?" .)
(Other definitions for under-the-table that I've seen before include "Illicit; hopelessly drunk" , "Not above board" , "Hush-hush" , "Transacted in secret -- sozzled" .)