Emphasise end of holidays, and lock (6)
I believe the answer is:
stress
'emphasise' is the definition.
(I've seen this before)
'end of holidays and lock' is the wordplay.
'end of' says to take the final letters.
'and' means one lot of letters go next to another.
'lock' becomes 'tress' (I've seen this before).
The final letter of 'holidays' is 's'.
's'+'tress'='STRESS'
(Other definitions for stress that I've seen before include "Tension; emphasis" , "Tension - accent" , "possible cause of fracture?" , "Lay emphasis on - it's a strain" , "suffering" .)