Keeping tender leads to love if one shows desire (6)
I believe the answer is:
libido
'desire' is the definition.
(I know that libido is a type of desire)
'keeping tender leads to love if one' is the wordplay.
'keeping' means one lot of letters goes inside another (some letters kept inside).
'tender' becomes 'bid' (synonyms).
'leads to' indicates taking the first letters.
The first letters of 'love if one' is 'lio'.
'bid' put within 'lio' is 'LIBIDO'.
'shows' is the link.
(Other definitions for libido that I've seen before include "Sexual impulse" , "Strong urge" , "Vital urge" , "Psychic, sexual, energy" , "Emotional energy associated with sexual desire" .)