Bodies not disposed to make a useful contribution (2,4,3)
I believe the answer is:
do ones bit
'make a useful contribution' is the definition.
(I've seen this before)
'bodies not disposed' is the wordplay.
'disposed' indicates anagramming the letters.
'bodies'+'not'='bodiesnot'
'bodiesnot' with letters rearranged gives 'DO ONES BIT'.
'to' acts as a link.
(Other definitions for do ones bit that I've seen before include "Contribute fairly for the common good" , "Take on a fair share" , "to perform as required" , "chip in" , "Contribute to effort" .)