Ryan Seacrest -- New Year's Eve Will be a CELEBRATION of Dick Clark

Ryan Seacrest tells TMZ ... the countdown to 2013 will be a special one, because he'll be honoring his late friend and mentor ... the great Dick Clark.

Seacrest was leaving a birthday lunch at Cecconi's in West Hollywood when we asked him how he felt about this year's NYE show .... the first one since Dick passed away back in April.

"I miss him," Seacrest told us ... adding, "I'm excited about New Year's though to celebrate him ... it'll be a fun night."

Clark hand-selected Seacrest to take over the main hosting gig on New Year's Rockin' Eve after he suffered a stroke back in 2004.