Twenty-six solutions, not further defined, are partners in familiar pairings. The required entry in the grid for each of these clues is the other partner. (Letter counts are for the words to be entered.)
3d President Kennedy ultimately dogged (6-4) For the grid entry i have ?R???T????
13d Three cobblers catch a cold (5) grid entry starts with P
20a Bill lines up lectures (5) accounts??
Normal clue :18d A bore stops ruminant pet on the way (4,4) ???? / ??G?
3 The answer to the clue itself is 5 -6.You need one of the recent US presidents, followed by 'Kennedy finally'. The second word means dogged, followed.
18 Road Rage, a pet/tantrum on the road.
13 'Three cobblers' indicates an anagram - of that word plus A + C(old).
20 A. The bill's an Ad, rather than an Ac, followed by a 7-letter word for 'lines up'.