Stuck on last (apparently inexplicable) three
I admit that soem of the letters I have may be erroneous :
20D - Observation's received about river blockage : it's in the Seine (5,4)
N-T-E / ---E
34A - Express a thought inconclusively in America (9)
S---E-I-E
36A - viscous lump left in trap (4)
-L-B