Deep affection (4)
I believe the answer is:
love
'deep affection' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for love that I've seen before include "See 10" , "1970 film, starring Ali MacGraw and Ryan O'Neal" , "Zero (tennis) four Dn" , "angel" , "See 23" .)