Grab hold of a first-class light source (5)

I believe the answer is:

clamp

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'grab hold' is the definition.
'clamp' can be an answer for 'hold' (thesaurus). I'm not sure about the 'grab' bit.

'a first-class light source' is the wordplay.
'a first class' becomes 'c' (1st letter of 'class').
'light source' becomes 'lamp' (I've seen this before).
'c'+'lamp'='CLAMP'

'of' is the link.

Can you help me to learn more?

(Other definitions for clamp that I've seen before include "Big, important" , "bracket" , "Fix firmly" , "Grip firmly" , "squeeze" .)

I've seen this clue in the Sydney Morning Herald.

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