Ignoring outsiders, Ethel's parents get cracking and tackle a problem (5,3,6)
I believe the answer is:
grasp the nettle
'tackle a problem' is the definition.
(to grasp the nettle is to tackle a difficult issue)
'ignoring outsiders ethel's parents get cracking' is the wordplay.
'ignoring outsiders' indicates the central letters.
'cracking' is an anagram indicator.
The central letters of 'ethels' are 'thel'.
'thel'+'parents'+'get'='thelparentsget'
'thelparentsget' anagrammed gives 'GRASP THE NETTLE'.
'and' acts as a link.
(Other definitions for grasp the nettle that I've seen before include "Boldly confront" , "likelihood of stingy response?" , "do some weeding?" , "taking stingy type in hand" , "Act boldly" .)