Pull everything in that's fat (6)
I believe the answer is:
tallow
'fat' is the definition.
(thesaurus)
'pull everything in' is the wordplay.
'pull' becomes 'tow' (tow is a kind of pull).
'everything' becomes 'all' (I've seen this before).
'in' is an insertion indicator.
'tow' going around 'all' is 'TALLOW'.
'that's' acts as a link.
(Other definitions for tallow that I've seen before include "Soap ingredient" , "Candle wax" , "Rendered fat used for making candles" , "Animal fat used to make ..." , "Candle ingredient" .)