Half-hearted tantrum flipping papers (5)
I believe the answer is:
tepid
'half-hearted' is the definition.
(I've seen this before)
'tantrum flipping papers' is the wordplay.
'tantrum' becomes 'pet'.
'flipping' shows that the letters should be reversed in order.
'papers' becomes 'ID' (identifying documents are one's 'papers').
'pet' reversed gives 'tep'.
'tep'+'id'='TEPID'
(Other definitions for tepid that I've seen before include "Showing little interest or enthusiasm" , "Moderately warm" , "Luke warm" , "Not very warm (water)" , "without enthusiasm" .)