Retrieve mug hiding cache regularly (6)
I believe the answer is:
access
'retrieve' is the definition.
(accessing is a kind of retrieving)
'mug hiding cache regularly' is the wordplay.
'mug' becomes 'ass' (I've seen this before).
'hiding' means one lot of letters goes inside another.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'cache' are 'cce'.
'ass' placed around 'cce' is 'ACCESS'.
(Other definitions for access that I've seen before include "Entry (code)" , "Admission" , "Entrance or passage" , "Way of entering or leaving" , "Means or right of entry" .)