He left here to work in park (7)
I believe the answer is:
reserve
'park' is the definition.
(thesaurus)
'he left here to work' is the wordplay.
'left' indicates named letters should be taken away.
'to work' becomes 'serve' (serving is a kind of working).
'here' with 'he' taken away is 're'.
're'+'serve'='RESERVE'
'in' acts as a link.
(Other definitions for reserve that I've seen before include "Savings - book" , "Set aside - shyness" , "8 [RESTRAINT]" , "keep for oneself" , "Modesty- store" .)