Gratitude for increase in value (12)
I believe the answer is:
appreciation
This could be a double definition.
'gratitude' is the first definition.
(I've seen this before)
'increase in value' is the second definition.
'appreciation' can be an answer for 'increase' (appreciation is a kind of increase). I'm unsure of the 'in value' bit.
'for' is the link.
Can you help me to learn more?
(Other definitions for appreciation that I've seen before include "Rise" , "An expression of gratitude" , "Gratitude; increase in value" , "recognition" , "It is shown by applause" .)