Harrow uniform is tight at first on the inside (8)
I believe the answer is:
distress
'harrow' is the definition.
(thesaurus)
'uniform is tight at first on the inside' is the wordplay.
'uniform' becomes 'dress' (dress uniform is a kind of uniform**).
'at first' says to take the initial letters.
'on the inside' is an insertion indicator.
The first letter of 'tight' is 't'.
'is'+'t'='ist'
'dress' enclosing 'ist' is 'DISTRESS'.
(Other definitions for distress that I've seen before include "Extreme anxiety or pain" , "Severe pain" , "Extreme anxiety or sorrow" , "Upset" , "State of suffering" .)