Ken, I'm in U-boat, unusual form of transport (8,4)
I believe the answer is:
mountain bike
'transport' is the definition.
(mountain bike is a kind of transport)
'ken i'm in u-boat unusual form' is the wordplay.
'unusual form' indicates anagramming the letters (I've seen this in other clues).
'ken'+'im'+'in'+'u'+'boat'='keniminuboat'
'keniminuboat' is an anagram of 'MOUNTAIN BIKE'.
'of' is the link.
(Other definitions for mountain bike that I've seen before include "Off-road cycle" , "Two-wheeler designed for rough terrain" .)