RAF Airfield Defence training in 1941

[Stirrick]

I have an airman who did his basic training at 12 Recruit Centre over June-July,1941.
And subsequently specialised as a Ground Gunner.

After 12RC he was posted to 11 Flying Training School at Shawbury.
Under this posting is a note stating "AA (D) Flight".

So, my question is, was this a Flight of 11 FTS which provided air defence for the station ?
In which case this airman would have been picking up the role 'on-the-job'.
Or was AA (D) a training Flight within 11 FTS ?

His next posting was to 1 Ground Gunnery School in June,1942.
By which time, of course, the RAF Regiment had been formed.
And so I presume that this is where he received formal AA Gunnery training ?

As always, I'd be grateful for any pointers.

[Stirrick]

Some other terms from his Service Record that I've not come across before.

Complexion = High COI
His first Good Conduct Badge is summarised in the 'Miscellaneous' section but prefixed by 'WS1'
Also in Miscellaneous - Med.Cat: Gunner 'V'
In the Reason column for postings - 'Form' and also 'RAFR'
And annotated at the end of the list of postings, are rows marked 'PR' and 'KMF 44'

Anybody come across these before ?