Loafer that's not suitable for express train? (9)
I believe the answer is:
slowcoach
'loafer' is the definition.
(I know that slowcoach is a type of dawdler)
'not suitable for express train?' is the wordplay.
'not suitable for express' becomes 'slow' (I can't justify this - if you can you should believe this answer much more).
'train?' becomes 'coach' ('coach' can be a synonym of 'train').
'slow'+'coach'='SLOWCOACH'
'that's' is the link.
Can you help me to learn more?
(Other definitions for slowcoach that I've seen before include "One who's not very fast" , "Laggard" , "Not a rapid operator" , "One who lacks liveliness, like old vehicle" , "Snail" .)