Some began slowly raising difficulty (4)
I believe the answer is:
snag
'difficulty' is the definition.
(I know that snag is a type of obstacle)
'some began slowly raising' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'raising' says the letters should be written in reverse.
'gans' can be found hidden inside 'began slowly'.
'gans' reversed gives 'SNAG'.
(Other definitions for snag that I've seen before include "Catch - disadvantage" , "Hidden obstacle or catch" , "Minor hitch" , "Glitch" , "Rip or tear" .)