Out of sorts around start of partial fast (6)
I believe the answer is:
speedy
'fast' is the definition.
('speedy' can be similar in meaning to 'fast')
'out of sorts around start of partial' is the wordplay.
'out of sorts' becomes 'seedy' (I've seen this before).
'around' is an insertion indicator.
'start of' suggests taking the first letters.
The initial letter of 'partial' is 'p'.
'seedy' enclosing 'p' is 'SPEEDY'.
(Other definitions for speedy that I've seen before include "Fast-moving" , "in a fast car?" , "'Fast, without delay (6)'" , "Quick" , "Express" .)