Master some sticky matter — regret speaking out (4)
I believe the answer is:
guru
'master' is the definition.
(religious master)
'some sticky matter regret speaking out' is the wordplay.
I cannot really see how this works, but
'matter' could be 'ru' (Ru is an example) and 'ru' is located in the answer.
The remaining letters 'gu' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for guru that I've seen before include "Swami" , "Influential expert" , "Hindu or Buddhist spiritual teacher" , "Hindu sage" , "Authoritative source" .)