Nice to 'see' you all. Thank you for having a go.
I never spotted 'tread on' and see where it could be quite acceptable,
I had 'trade on' because it has its own listing in Chambers where 'tread on' does not.
There's no need to post my workings as ab, djaw and Tony have explained all (even though there's the wee matter of tread/trade. I'll post 'em anyway, just for completion:-
1. anag (in a maze) of “a rodent” = TRADE ON = take advantage of (Chambers Dictionary)
2. members = legs; one on = i + on; leg(ion)s = LEGIONS = old divisions
3. (cryptic and double) name of bar in US ‘comedy soap opera’ = CHEERS = Cheers! = Good health!
4. Complex anag (and becomes) of “unquestionable” – “ Queen” = USAIN BOLT
(Couldn't resist it!)
5. sailor = tar; repeatedly = tartar + E (drug) = TARTARE + sauce(lip) = TARTARE SAUCE = dressing.