Speak indistinctly, having had a double rum set up? (6)
I believe the answer is:
murmur
'speak indistinctly' is the definition.
(synonyms)
'double rum set up?' is the wordplay.
'double' says to double the letters.
'set up?' is a reversal indicator (in a down clue, letters go up).
'rum' back-to-front is 'mur'.
'mur' doubled is 'MURMUR'.
'having had a' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for murmur that I've seen before include "Undertone" , "Indistinct mutter" , "Low, indistinct speech" , "Mumbled expression of malcontent" , "Soft voices (of discontent)" .)