Female isn't passionate about king that's timid (5-7)
I believe the answer is:
faint-hearted
'timid' is the definition.
(I've seen this before)
'female isn't passionate about king' is the subsidiary indication.
'female' becomes 'f' (abbreviation).
'isn't' becomes 'aint' (I've seen this before).
'passionate' becomes 'heated' ('heated' can be similar in meaning to 'passionate'**).
'about' means one lot of letters goes inside another.
'king' becomes 'r' (r is abbreviation for rex).
'heated' going around 'r' is 'hearted'.
'f'+'aint'+'hearted'='fainthearted'
'that's' is the link.
(Other definitions for faint-hearted that I've seen before include "Timorous - find a theatre (anag)" , "Timid" , "chicken" .)