Bicycle for two (6)
I believe the answer is:
tandem
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bicycle for two</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tandem that I've seen before include "Bike with two saddles" , "Two-seater bike" , "Two-person bike" , "Two-seater bicycle" , "One behind another, as on bicycle" .)