When keeping cover, reportedly is of use (6)
I believe the answer is:
avails
'is of use' is the definition.
(I've seen this before)
'when keeping cover reportedly' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'keeping' indicates putting letters inside (some letters kept inside).
'cover reportedly' becomes 'vail' (I can't justify this - if you can you should believe this answer much more).
'as' enclosing 'vail' is 'AVAILS'.
Can you help me to learn more?
(Other definitions for avails that I've seen before include "Makes use of saliva" , "Is of profit, helps" , "Takes advantage of or benefits from" .)