Father, I conclude, extremely likely to be warm (8)
I believe the answer is:
friendly
'warm' is the definition.
(synonyms)
'father i conclude extremely likely' is the wordplay.
'father' becomes 'fr' (abbreviation as in a priest's title).
'conclude' becomes 'end' (I've seen this in another clue).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'likely' with its middle removed is 'ly'.
'fr'+'i'+'end'+'ly'='FRIENDLY'
'to be' acts as a link.
(Other definitions for friendly that I've seen before include "such a society" , "match?" , "Sociable" , "Affable" , "Amiable" .)