Chocolate cake indicates what good deeds can earn you? (7,6)
I believe the answer is:
brownie points
'what good deeds can earn you?' is the definition.
'chocolate cake indicates' is the wordplay.
'chocolate cake' becomes 'brownie' (I've seen this before).
'indicates' becomes 'points' ('point' can be a synonym of 'indicate').
'brownie'+'points'='BROWNIE POINTS'
(Other definitions for brownie points that I've seen before include "Marks gained for good behaviour" , "Marks earned for doing right?" , "Credit for doing well" , "Notional awards for good work" , "approbation" .)