Tools from retro section of aisle worthless (7)
I believe the answer is:
trowels
'tools' is the definition.
(trowel is a kind of tool)
'retro section of aisle worthless' is the wordplay.
'retro' says the letters should be written in reverse (retro is Latin for 'backwards').
'section of' says the answer is hidden in the clue.
'slewort' is hidden within 'aisle worthless'.
'slewort' back-to-front is 'TROWELS'.
'from' is the link.
(Other definitions for trowels that I've seen before include "Small hand tools" , "Hand tools for scooping" , "Garden tools" , "Garden implements" , "Tools for gardening and plastering" .)