I'm finding this extremely difficult, struggling even to parse some of the answers I think I've got.
1a Grit discernible after emptying the sack (13)
Determination fits.
26a Very different pictures on pavement, say around drain (7,5)
Streets apart?
38d Granny's getting into airline stock which may lead to downfall (6,4)
Banana skin? But how do we get skin?