Fortune made at the start of the year, before a temporary drop - this game is sometimes rewarding (5,3)
I believe the answer is:
lucky dip
'a temporary drop this game is sometimes rewarding' is the definition.
The definition suggests a singular noun which matches the answer.
'fortune made at the start of the year' is the wordplay.
'fortune' becomes 'luck' (synonyms).
'made' becomes 'dip' (I am not sure about this - if you are sure you should believe this answer much more).
'at' says to put letters next to each other (I've seen this in other clues).
'the start of' suggests taking the first letters.
The initial letter of 'year' is 'y'.
'dip' after 'y' is 'ydip'.
'luck'+'ydip'='LUCKY DIP'
'before' is the link.
Can you help me to learn more?
(Other definitions for lucky dip that I've seen before include "speculation" , "pick at random here?" , "Container with articles of various values for random choice" , "Box filled with sawdust hiding prizes" , "Eg, bran tub" .)