Threaten one member with dissolution (6)
I believe the answer is:
impend
'threaten' is the definition.
(I've seen this in another clue)
'one member with dissolution' is the wordplay.
'one' becomes 'i' (Roman numeral).
'member' becomes 'MP' (Member of Parliament).
'with' means one lot of letters go next to another.
'dissolution' becomes 'end' (I've seen this in other clues).
'i'+'mp'+'end'='IMPEND'
(Other definitions for impend that I've seen before include "Be looming" , "Be imminent or about to happen" , "menace" , "(Of a bad thing) loom" , "Threaten - be about to happen" .)