Love but no husband for this regretful lady (4)
I believe the answer is:
otis
'this regretful lady' is the definition.
(Miss Otis Regrets is a song by Cole Porter)
'love but no husband' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'but no husband' becomes 'tis' (I can't justify this - if you can you should give a lot more credence to this answer).
'o'+'tis'='OTIS'
'for' is the link.
Can you help me to learn more?
(Other definitions for otis that I've seen before include "Regretful miss" , "Company providing lifts" , "Lift man" , "Place of worship; side part of head" , "- - Redding (soul music star)" .)