8a...Receptacle for the last part to wriggle in(5)...?R???
17a...This English is American(5)...?A?A?
2d...A tailor's turn-over(5)...?A???
4d...The last letter of it abuts on one(4)...??G?
Legitim..a good suggestion but wouldn't fit in with other answers e.g. 21a It is an impediment so to speak...STUTTER..S & T are definite, the second T is in NATTY and the E in LEGATEE