Loco senior dancing around short nude (4,5)
I believe the answer is:
iron horse
'loco' is the definition.
(I've seen this before)
'senior dancing around short nude' is the wordplay.
'dancing' indicates an anagram.
'around' indicates putting letters inside.
'nude' says to take the centre (the word is stripped of its outer letters).
The central letters of 'short' are 'hor'.
'senior' is an anagram of 'ironse'.
'ironse' going around 'hor' is 'IRON HORSE'.
(Other definitions for iron horse that I've seen before include "worn-out engine" , "Old name for locomotive" , "one's gone off the rails" , "Steam locomotive" , "film once in America!" .)