Wall Street Journal hints (April 18, 2015)

Great variety cryptic by Hex in this weekend’s Wall Street Journal!  All the words have to be altered before entry, according to a formula provided in a superfluous word added to the respective clue.  Not too hard, not too easy—a perfect introduction to variety cryptics.

Below the fold is a set of hints in case you need them.  Click and drag over the respective box to see what the superfluous word is in each clue and how to interpret it.

Wall Street Journal hint: 4/18/15 

Across			Down
1	IM parts		1	CHA in
4	TRA in		2	ARO used
10	bar B		3	strike R
12	final E		4	P added
13	B out		5	R enters
15	TIME out		6	steal TH
16	and Y		7	P out
17	plus H		8	ANTI gone
18	M ending		9	minus CULE
21	in CA		11	E as T
24	L out		14	D inner
28	erase R		19	append AGES
31	L is P		20	RA in
33	B less		22	SE away
35	add ER		23	D over
36	WYO missing		25	no T
37	S on		26	W in
38	R is E		27	in SET
39	ER in		29	G in
40	scrap E		30	C leaving
			32	M as T
			34	strip E