Is the tight end an eligible receiver if he is covered by a wide receiver?

If the split end is on the line, no. If this wideout is actually a flanker - not on the line, then that would put the TE on the end making him eligible. A tight end is called an end because he is on the end of the line. Eligible receivers are all players in the backfield (not on the line of scrimmage), plus the the two linemen that are on each end of the line. The other requirement for eligibles is that they be numbered 1-49 or 80-99. A common foul is when a wide out lines up on the end of the line on the same side as the tight end, then a tight end is downfield (beyond the expanded 2 yard neutral zone) goes downfield while a forward pass travels beyond the line of scrimmage. In this case, the wide out erred in lining up wrong, or the tight end should have known he was covered and thus ineligible.