Sweet, warm hearted, silly Gus (5)
I believe the answer is:
sugar
'sweet' is the definition.
(thesaurus)
'hearted silly gus' is the wordplay.
'hearted' says to take the centre.
'silly' becomes 'absurd' (I've seen this before).
'gus' becomes 'gar' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The centre of 'absurd' is 'su'.
'su'+'gar'='SUGAR'
'warm' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for sugar that I've seen before include "See 11" , "Term of affection" , "Damn" , "Basic sweetener" , "Sweeten" .)