1: Its a firm, small lettuce (3)
2: Exegesis of clue an idiot misunderstood (11)
3: Privy to accessibility (11)
4: They secure money for the government, so we hear (5)
5: Civil libertarian sends building uprights (4,5)
6: Picture a dessert without topping (3)
7: Small piece of fish (3)
8: Employ heart-broken Spartans where disaster came to pass. (11)
11: Toss a hammer into a nuclear accelerator! (4,7)
13: Exchange concealed proprietary knowledge (5,6)
14: Everyone in Italy's mad - so it's said - for ice cream (5-6)
16: Secret art dashed Tennessees desire (9)
22: Defame how I live in 16-across local (5)
25: Complain about the horse (3)
26: Choose to take the top off (3)
28: Nothing we have to pay (3)