Gather fuel round lake (5)
I believe the answer is:
pleat
'gather' is the definition.
(thesaurus)
'fuel round lake' is the wordplay.
'fuel' becomes 'peat' (peat is a kind of fuel**).
'round' means one lot of letters goes inside another.
'lake' becomes 'l'.
'peat' placed around 'l' is 'PLEAT'.
(Other definitions for pleat that I've seen before include "Fold pressed or stitched into cloth" , "Fold in clothing" , "Fold sewn or pressed into cloth" , "Gathering" , "Flat fold of cloth" .)