Gather organic fuel round lake (5)
I believe the answer is:
pleat
'gather' is the definition.
(thesaurus)
'organic fuel round lake' is the wordplay.
'organic fuel' becomes 'peat' (I've seen this before**).
'round' indicates putting letters inside.
'lake' becomes 'l'.
'peat' enclosing 'l' is 'PLEAT'.
(Other definitions for pleat that I've seen before include "that's tailor-made" , "Fold pressed or stitched into cloth" , "Double fold in a garment" , "Fold in material" , "Tuck" .)