Starts to prevaricate over man in trouble — flipping fatty lump (6)
I believe the answer is:
lipoma
'fatty lump' is the definition.
(a lipoma is a lump of fat)
'starts to prevaricate over man in trouble flipping' is the wordplay.
'starts to' indicates taking the first letters.
'in' indicates putting letters inside.
'trouble' becomes 'ail' (synonyms).
'flipping' says the letters should be written backwards.
The initial letters of 'prevaricate over man' is 'pom'.
'ail' back-to-front is 'lia'.
'pom' inserted inside 'lia' is 'LIPOMA'.
(Other definitions for lipoma that I've seen before include "Adipose tumour" , "swelling" , "Fat lump" .)