instead; but (on the other hand)
Used to introduce an alternative, a trade-off, or a contrasting point. Often implies that something is given up or exchanged for something else.
今日は忙しいから、その代わり明日手伝うよ。
I'm busy today, so instead I'll help you tomorrow.
This apartment is far from the station, but on the other hand the rent is cheap.
From その (that) + 代わり (substitute, replacement). Literally 'as a substitute for that'.