Progressing slowly (7)
I believe the answer is:
gradual
'progressing slowly' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for gradual that I've seen before include "(Of slope) not steep" , "Bit by bit" , "By easy stages, not sudden or steep" , "Little-by-little" , "Happening slowly and by degrees" .)