The 23-year-old saw his recent string of fine performances rewarded when he was named in the Red Rose Six Nations squad on Wednesday.
He has been picked as a lock for the tournament which kicks off on February 2 as England take on Scotland at Twickenham.
And Clark feels the demands at Saints, where expectations are high following a fine win at Exeter last weekend, have brought the best out of him.
“I think each year we get thrown new challenges and as a player it’s a good environment to be in,” said Clark, who lines up for Saints against Castres in the Heineken Cup on Friday night.
“It’s quite a high pressure environment to be in and you have to perform each week to get picked.
“That’s really positive and going to help us moving forward.”
Clark only returned to the side in November following the conclusion of the 32-week ban he picked up in March for an incident involving Leicester Tigers hooker Rob Hawkins.
But he has been impressive ever since, showing his immense will to win in every game and taking matches by the scruff of the neck, notably at Exeter last weekend.
“I’m really pleased,” said Clark when asked about his form. “It’s great to be in the side and playing with all the lads.
“The season’s been a bit hit and miss, we’ve not had all the results we wanted but we keep going, we keep believing and we hope it comes right for us.”