Travelling actor is one with a considerable vocabulary of expletives, we hear! (7)
I believe the answer is:
trouper
'travelling actor' is the definition.
'trouper' can be an answer for 'actor' (trouper is a kind of actor). I am unsure of the 'travelling' bit.
'one with a considerable vocabulary of expletives we hear' is the wordplay.
I cannot quite see how this works, but
'one' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is present in the answer.
This explanation may well be incorrect...
'is' acts as a link.
Can you help me to learn more?
(Other definitions for trouper that I've seen before include "actor" , "long-term impersonator" , "Travelling performer" , "Loyal, hard-working type" , "Old stager" .)