Frequent tours become hard for invader of Roman Empire (8)
I believe the answer is:
visigoth
'invader of roman empire' is the definition.
'visigoth' can be an answer for 'invader' (I have seen 'European invader ' mean 'visigoth' so perhaps 'invader' could also mean 'visigoth'). I am unsure of the 'of roman empire' bit.
'frequent tours become hard' is the wordplay.
'frequent' becomes 'visit' (I can't explain this - if you can you should believe this answer much more).
'tours' is an insertion indicator (tour can mean to go around).
'become' becomes 'go' (eg to go rotten is to become rotten).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'visit' placed around 'go' is 'visigot'.
'visigot'+'h'='VISIGOTH'
'for' is the link.
Can you help me to learn more?
(Other definitions for visigoth that I've seen before include "he had a smashing time in Rome" , "Old European" , "Early settler" , "Spanish settler" , "Alaric, eg, who conquered Rome" .)