Absolutely ludicrously hot inside pastry that's flipped over (3,4)
I believe the answer is:
not half
'absolutely' is the definition.
(I've seen this before)
'ludicrously hot inside pastry that's flipped over' is the wordplay.
'ludicrously' indicates an anagram (I've seen this in other clues).
'inside' indicates putting letters inside.
'pastry' becomes 'flan' (I've seen this in another clue).
'that's flipped over' is a reversal indicator.
'flan' reversed gives 'nalf'.
'hot' anagrammed gives 'oth'.
'oth' placed inside 'nalf' is 'NOT HALF'.
(Other definitions for not half that I've seen before include "To an extreme degree" , "One hundred per cent!" , "like a bigger drink?" , "I warmly agree!" , "less than fifty per cent" .)