Speaker systems cause anger in travellers after vacation (7)
I believe the answer is:
tannoys
'speaker systems' is the definition.
(tannoy is a speaker system)
'cause anger in travellers after vacation' is the wordplay.
'cause anger' becomes 'annoy' (to annoy is to anger someone).
'in' means one lot of letters goes inside another.
'after vacation' means to remove the middle letters (the inside letters must vacate).
'travellers' with its centre removed is 'ts'.
'annoy' placed inside 'ts' is 'TANNOYS'.
(Another definition for tannoys that I've seen is " Loudspeaker systems".)