Two-seater bicycle (6)
I believe the answer is:
tandem
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">two-seater bicycle</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tandem that I've seen before include "Bike for two cyclists" , "Two-seater bicycle" , "it's not normally what one rides" , "Bike with two saddles" , "Two-seater bike" .)