We can't be sure the answer is accurate without knowing the following words. Consign is one possibility.
day
daydaylightdaybreakdaytime
out
day
The word is "land." I realize that's not three letters.
con + sign = consign
con-sign
We can't answer that unless you tell us the following words.
pro, con
day
con consign, conduct, confound, contract ect.....
We won't be able to answer this accurately if you don't tell us the following words.