It's normal to open the middle of three 4-card suits when you have a black singleton.

South will just show her 4-card Spade suit. 1♠ is forcing so she knows she will have a chance to show her srength later.

North likes Spades, but how excited should North be?

If you're using the Losing Trick Count then North has a LTC=6. Assuming south has LTC=9 for a simple response then 3♠ is the right bid. 9+6=15 and 18-15=3.

If you're not using the LTC North should still upgrade their hand because of the Club singleton but only by 2-3 points. That's not enough for North to be confident of game over just 6 points so again 3♠ is the best bid

South does have a Losing Trick Count of 9 so will pass if using that method. However if you're not using the LTC then South should accept the invitation and bid 4♠ 

Did you think of bidding 4♥ ? Maybe you thought that North would have 5 cards in their first suit? If so remember that is an 'almost always' rule. The exception being the 4.4.4.1 shape. Also even if Norh does have five Hearts it is usually better to play in a 4-4 fit than a 5-3 one as the 5-3 suit gives you a chance to discard losers in a side suit.

Making 4♠ isn't easy. Best defence looks like leading a Spade initially and then another one when in with ♣ A. This defence, together with the ♣ A offside and a 4-1 trump break makes communication hard for declarer. Best plan initially is probably to try and ruff two locing Clubs. However declarer will do best to switch to Plan B - ruff one Club loser, draw trumps and hope the ♥ J dropd in hree rounds, which it does.