Made a comparison with light surrounding president Nixon's head (7)
I believe the answer is:
likened
'made a comparison' is the definition.
The definition and answer can be both related to thinking as well as being past participle verbs.
Maybe you can see a link between them that I can't see?
'light surrounding president nixon's head' is the wordplay.
'light' becomes 'led' (light-emitting diode).
'surrounding' means one lot of letters goes inside another.
'president' becomes 'ike' (nickname of Dwight Eisenhower).
'head' says to take the initial letters.
The first letter of 'nixon' is 'n'.
'ike'+'n'='iken'
'led' enclosing 'iken' is 'LIKENED'.
'with' is the link.
Can you help me to learn more?
(Other definitions for likened that I've seen before include "Resembled" , "Pointed out resemblance or compared" , "Equated" .)