What it cost to write to New York? (5)
I believe the answer is:
penny
'what it cost' is the definition.
I can't judge whether this defines the answer.
'write to new york?' is the wordplay.
'write' becomes 'pen' (synonyms).
'to new york?' becomes 'ny'.
'pen'+'ny'='PENNY'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for penny that I've seen before include "1p" , "coin, decimal with 1a [NEW]" , "Coin spent by the desperate?" , "one might drop" , "One hundredth of a pound" .)