Almost link up with love (3)
I believe the answer is:
nil
'love' is the definition.
(I've seen this before)
'almost link up' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'up' is a reversal indicator (in down clue: letters go upwards).
'link' with its last letter removed is 'lin'.
'lin' in reverse letter order is 'NIL'.
'with' acts as a link.
(Other definitions for nil that I've seen before include "Nothing, no score" , "Latin zero" , "Nothing, zero" , "none" , "Lacking value" .)