Philosophical line in cost adjustment (5)

I believe the answer is:

stoic

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'philosophical' is the definition.
(thesaurus)

'line in cost adjustment' is the wordplay.
'line' becomes 'i' (I can't justify this - if you can you should believe this answer much more).
'in' means one lot of letters goes inside another.
'adjustment' indicates an anagram.
'cost' anagrammed gives 'stoc'.
'i' going within 'stoc' is 'STOIC'.

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(Other definitions for stoic that I've seen before include "Philosopher like Marcus Aurelius" , "Solemn ceremony" , "One indifferent to fortune, pleasure and pain" , "One who doesn't complain" , "Greek philosopher" .)

I've seen this clue in the Evening Standard.

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