It's philosophically rational to give thanks for love (3)
I believe the answer is:
tao
'it's philosophically rational to' is the definition.
I can't judge whether this definition defines the answer.
'thanks for love' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'for' is a charade indicator (letters next to each other).
'love' becomes 'o' (love means zero in tennis).
'ta'+'o'='TAO'
'give' is the link.
Can you help me to learn more?
(Other definitions for tao that I've seen before include "Source of existence (Chinese)" , "true path" , "path of Chinese" , "Chinese philosophical principle" , "In China, code of behaviour in harmony with natural order" .)