Gitto
39A - the thematic item here was unfamiliar to me. Def is first 2 words; synonym of next 2 words goes inside 'riverless' spas.
30D - can't really add anything to what's said below - the last 4 words of the clue (wordplay) give , IMO, a fairly obscure indication to the last 4 letters of the answer.
4D - abbreviation inside 6-letter word meaning 'of those folk'