Worked hard to initially install light (6)
I believe the answer is:
toiled
'worked hard' is the definition.
(I've seen this before)
'to initially install light' is the wordplay.
'initially' suggests taking the first letters.
'light' becomes 'led' (I've seen this in other clues**).
The first letter of 'install' is 'i'.
'to'+'i'+'led'='TOILED'
(Other definitions for toiled that I've seen before include "Worked incessantly" , "Laboued long and hard" , "Worked long and hard" , "Worked or laboured very hard" , "Struggled long and hard" .)