Guided up endless dell (3)
I believe the answer is:
led
'guided' is the definition.
(similar in meaning)
'up endless dell' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'endless' means to remove the last letter.
'dell' with its final letter removed is 'del'.
'del' backwards is 'LED'.
(Other definitions for led that I've seen before include "Something emitting light" , "Went ahead" , "Conducted" , "Went in advance of others" , "Guided; small light" .)