1: I had left mule, finally, and right loafer (5)
4: Ideas about teaching assistant marginalia (9)
8: Chewed-up gum in tater -- how toothsome (5-8)
10: Trains without commanding officer and suffers (5)
12: Catch first fish? Hold fast (5)
13: Put a new value on what secret agent is hiding (5)
15: Man arrives at a low scrubland (9)
16: Fair sort one fleeing SAAB/Holden prang (3,6)
18: Adds money owed to the government in hearing (5)
20: Mousy girlfriend loses head and bellybutton (5)
21: Perhaps a bathroom contractor is mentioned to a former president (5)
23: Nick shouts - and theres trouble brewing! (3,5,2,3)
25: Had to be infatuated (9)
26: Lustful inside, eager and young (5)