Little difficulty raising source of water (4)
I believe the answer is:
spat
'little' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'difficulty raising source of water' is the wordplay.
'difficulty' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'raising' shows that the letters should be reversed in order (in a down clue, letters go up).
'source of water' becomes 'tap' (I've seen this in another clue).
'tap' reversed gives 'pat'.
's'+'pat'='SPAT'
Can you help me to learn more?
(Other definitions for spat that I've seen before include "Old-fashioned legwear" , "Quarrel about petty point" , "cross words" , "Bickering" , "Little quarrel - leg wear" .)