The Big One

[Jaimsieboy]

2 Down - Shallow pies (5) T????
18 Across - Gaiety (8) M???a?e??
16 Across - Cotton on (7) ????i?e
17 Across - Obsessive love for ones self (8) E???????

[writesbad]

2 tarts

[squarebear]

18d merriment?

[squarebear]

16a realise?

[mygirl]

17a egomania

[octogenarian]

2d Tarts--------17a Egoistic

[dtgblue]

egotism not enough letters though

[sandyRoe]

if 17a is 7 rather than 8 it could be Egotism

[emeritus]

17a Egoistic

[daftgrandad]

2 Tarts
18 Merriment
16 Realise
17 Egoistic

[TOMMO33]

17a must be as noun, so egomania more likely.

[writesbad]

Jaimsie, for 18a you've said eight letters, but put nine in your part answer. Which is it?

[nightmare]

err,
egoistic is an adjective.
I agree with mygirl - egomania