Cover too many a circuit (7)
I believe the answer is:
overlap
'cover' is the definition.
(overlapping is a kind of covering)
'too many a circuit' is the wordplay.
'too many' becomes 'over' (I've seen this in other clues).
'a circuit' becomes 'lap' ('lap' can be a synonym of 'circuit').
'over'+'lap'='OVERLAP'
(Other definitions for overlap that I've seen before include "Coincide in part" , "Rest one on another" , "Outflank" , "Partially coincide" , "Project" .)