Endeavour shown by office worker welcomed by a disheartened typist (7)
I believe the answer is:
attempt
'endeavour' is the definition.
('attempt' can be a synonym of 'endeavour')
'office worker welcomed by a disheartened typist' is the wordplay.
'office worker' becomes 'temp' (I've seen this before).
'welcomed by' indicates putting letters inside (I've seen this in other clues).
'disheartened' says to hollow out the word (remove centre letters).
'typist' with its centre taken out is 'tt'.
'a'+'tt'='att'
'temp' going into 'att' is 'ATTEMPT'.
'shown by' is the link.
(Other definitions for attempt that I've seen before include "Shot" , "Tackle" , "Try, make an effort" , "Essay" , "Stab" .)