Caustic about love? Humorist gets indication of fate (5,4)
I believe the answer is:
tarot card
'indication of fate' is the definition.
(tarot cards might indicate someone's fate)
'caustic about love? humorist' is the wordplay.
'caustic' becomes 'tart' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'love?' becomes 'o' (love means zero in tennis).
'humorist' becomes 'card' (card is a kind of humorist).
'tart' going around 'o' is 'tarot'.
'tarot'+'card'='TAROT CARD'
'gets' acts as a link.
(Other definitions for tarot card that I've seen before include "One from fortune-telling pack" , "fortune-teller in suit" , "Empress?" , "I forecast" .)