Dancing actress covers excellent steps (9)
I believe the answer is:
staircase
'steps' is the definition.
(I've seen this before)
'dancing actress covers excellent' is the wordplay.
'dancing' is an anagram indicator.
'covers' is an insertion indicator.
'excellent' becomes 'ai' (resembles 'A1', old-fashioned term for excellent).
'actress' is an anagram of 'strcase'.
'strcase' enclosing 'ai' is 'STAIRCASE'.
(Other definitions for staircase that I've seen before include "Way between floors" , "Indoor flight" , "Route between floors" , "Group of joined locks on a canal" , "A group of linked canal locks" .)