Not all hoboes trust heat (7)
I believe the answer is:
oestrus
'heat' is the definition.
(I know that heat can be written as oestrus)
'not all hoboes trust' is the wordplay.
'not all' indicates the answer is hidden within the clue (only some of the letters).
'OESTRUS' can be found hidden inside 'hoboes trust'.
(Other definitions for oestrus that I've seen before include "Sourest (anag.)" , "Heat" .)