It starts to trouble every task group (6)
I believe the answer is:
sextet
'group' is the definition.
The answer is an example.
'it starts to trouble every task' is the wordplay.
'it' becomes 'sex' ('it' is a common euphemism for sex).
'starts to' says to take the initial letters.
The initial letters of 'trouble every task' is 'tet'.
'sex'+'tet'='SEXTET'
(Other definitions for sextet that I've seen before include "Three couples" , "Musical work" , "Group of six performers" , "Musical group" , "Chamber group (1)" .)