Initially slimmer and fitter from cutting down on the grass (8)
I believe the answer is:
strimmer
'cutting down on the grass' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'initially slimmer and fitter' is the wordplay.
'initially' suggests taking the first letters.
'and' is a charade indicator (letters next to each other).
'fitter' becomes 'trimmer' ('trim' can be a synonym of 'fit').
The initial letter of 'slimmer' is 's'.
's'+'trimmer'='STRIMMER'
'from' is the link.
Can you help me to learn more?
(Other definitions for strimmer that I've seen before include "Machine for cutting grass edges" , "Brush cutter" , "Garden equipment" , "Gardening implement" , "Hand-held grass cutter" .)