Source thus claiming government department's in fits (9)
I believe the answer is:
spasmodic
'source thus claiming government department's in fits' is the definition.
I can't judge whether this definition defines the answer.
'source thus claiming government department's' is the wordplay.
'source' becomes 'spa' (I have seen 'source of water' mean 'spa' so perhaps 'source' could also mean 'spa').
'thus' becomes 'sic' ('thus' in Latin).
'claiming' means one lot of letters goes inside another.
'government department' becomes 'mod' (Ministry of Defence).
'sic' placed around 'mod' is 'smodic'.
'spa'+'smodic'='SPASMODIC'
Can you help me to learn more?
(Other definitions for spasmodic that I've seen before include "Intermittent" , "Occasional" , "fitfully" , "Done in brief irregular bursts" , "Occurring in irregular bursts" .)