After some early sparring, the first chance of the game went Linfield's way as Matthew Fitzpatrick unleashed a powerful strike after some nice work from Chris McKee, but he couldn't keep his effort down.
Five minutes before the break the visitors had their best chance of the first half, as substitute Paul O'Neill met Ryan's cross at the back post but couldn't generate enough power to really trouble David Walsh, who made a simple catch.
The big talking point of the first half was Ryan's red card just before the break, with referee Shane Andrews showing no hesitation in sending the Larne striker for an early shower after a strong tackle on McClean.
Linfield were determined to make their extra man count and did just that on the hour mark, as Offord opened his account with a cool finish through the legs of Rohan Ferguson.
That was his 11th Irish Premiership goal of the season, which was enough to seal all three points for the runaway leaders.