... fabricated cover lined with ermine's tail (4)
I believe the answer is:
lied
'fabricated' is the definition.
(I've seen this in another clue)
'cover lined with ermine's tail' is the wordplay.
'cover' becomes 'lid' (lid is a kind of cover).
'lined with' is an insertion indicator (as in being filled or lined with something).
'tail' suggests the final letters.
The last letter of 'ermine' is 'e'.
'lid' going around 'e' is 'LIED'.
(Other definitions for lied that I've seen before include "Art song - told porkies" , "Idle (anag.)" , "German art song" , "Told stories" , "Told untruths; song" .)