Someone who posted on X dismissing Welsh rock (6)
I believe the answer is:
teeter
'rock' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for teeter that I've seen before include "Balance unsteadily" , "Move with little assurance" , "Totter, wobble" , "waver" , "Stand or move unsteadily" .)