Walk with Muppetman to see Rocketman? (10)
I believe the answer is:
stephenson
'rocketman?' is the definition.
(Robert Stephenson, inventor of Stephenson's Rocket)
'walk with muppetman' is the wordplay.
'walk' becomes 'step' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'muppetman' becomes 'henson' (Jim Henson, creator of The Muppets).
'step'+'henson'='STEPHENSON'
'to see' is the link.
(Other definitions for stephenson that I've seen before include "Rocket engineer" , "Train man" , "man of note" , "Loco inventor" , "George --, rail pioneer" .)