Conclude covering Queen — Queen or Supergrass? (8)
I believe the answer is:
squealer
'supergrass?' is the definition.
(squealer can mean an informant)
'conclude covering queen queen' is the wordplay.
'conclude' becomes 'seal' (as in sealing the deal).
'covering' indicates putting letters inside.
'queen' becomes 'qu' (abbreviation for queen).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'seal' placed around 'qu' is 'squeal'.
'squeal'+'er'='SQUEALER'
'or' is the link.
(Other definitions for squealer that I've seen before include "Grass" , "One making high-pitched cry" , "Rat" , "Informer (what a swine!)" , "pig?" .)