One such word is whenever.
airtimeanytimebedtimedowntimelunchtimemealtimeovertimeplaytimesometimespringtimesummertimetimebasetimeouttimesharewintertime
roommate
a compound word beginning with cart is any word that begins with cart and has another word in it.
quiz off
Some compound words starting with under include:underbrushunderclothesundercookundercoverundercutunderdoneunderestimateundergoundergroundundergrowthunderdevelopedunderhandedunderlineunderlyingundermineundernourishedunderpaidunderpantsunderpinningunderplayunderperformedunderratedundershortsundershotundersideunderstandunderstateunderstoodundertakeundertowunderusedunderwear
Fallback is a compound word. Falloff and fallout are compound words.
The answer is become.
teardrop gumdrop raindrop dewdrop backdrop
Doable
zebralicious
airtimeanytimebedtimedowntimelunchtimemealtimeovertimeplaytimesometimespringtimesummertimetimebasetimeouttimesharewintertime
backbonebackgroundballparkbaseballbaseboardbasketballbathhousebathtubbathwaterbirdhousebirthdaybirthmarkbirthrightblackbirdblackboardblackmailbloodbathbookmarkbookshelfbluebellbluebirdblueprintboyhoodbrainwavebreadwinnerbreakwaterbrownstonebutterball
Snail
roommate
"Lukewarm."
crossroadrailroadroadblockroadsignsroadsideroadwayroadrunnerroadworkroadworthy
maidness