During a random chat the other day, an interesting question came up: suppose you are in a holding area within TMA, with a few aircraft below and above you, and TCAS suddenly says "Descend descend". What shall you do? A TCAS RA in such a situation is fairly likely to be irrelevant - for example,
this Eurocontrol study, albeit old, analysed 35 RAs in a hold and found 6 useful ones, 19 nuisance ones (i.e. dictated by TCAS logic but operationally unwarranted), 3 false ones, 4 RAs replicating ATC instructions already issued and 3 with insufficient data. On the other hand, a sudden descent with a stack of aircraft below you can cause more danger than it mitigates.
My idea would be to descend ~200 ft (so as not to trigger alarms below me), level out and transmit:
Pan-pan pan-pan pan-pan all stations, this is XX-XXX holding at YYY FL ZZ, getting TCAS RA to descend. All aircraft above FL ZZ over YYY check your altitude, then stand by to descend further or return to the assigned level. A critical discussion is welcome.