Goes slowly with an afterthought about an old wreck (5)
I believe the answer is:
plods
'goes slowly' is the definition.
Although both the answer and definition are verbs in their -s form, I can't understand how one could define the other.
'an afterthought about an old wreck' is the wordplay.
'an afterthought' becomes 'ps' (ps stands for postscript).
'about' means one lot of letters goes inside another.
'wreck' indicates an anagram.
'old' is an anagram of 'lod'.
'ps' enclosing 'lod' is 'PLODS'.
'with' acts as a link.
Can you help me to learn more?
(Another definition for plods that I've seen is " Trudges".)