Slave gathering in fine wrapping material (7)
I believe the answer is:
tinfoil
'wrapping material' is the definition.
(material which food is wrapped in)
'slave gathering in fine' is the wordplay.
'slave' becomes 'toil' (I've seen this in another clue).
'gathering' indicates putting letters inside (gather can mean to acquire or bring in).
'fine' becomes 'f' (abbreviation e.g. condition of old coins, books).
'in'+'f'='inf'
'toil' enclosing 'inf' is 'TINFOIL'.
(Other definitions for tinfoil that I've seen before include "Shiny food wrapping" , "up to wrapping up dope" , "Thin metallic sheet" , "This coverage" , "Thin metallic sheets for protecting food" .)