Help Dave's heart trouble (5)
I believe the answer is:
avail
'help' is the definition.
(I know that avail is a more specific form of help)
'dave's heart trouble' is the wordplay.
'heart' says to take the centre.
'trouble' becomes 'ail' (synonyms).
The middle of 'dave' is 'av'.
'av'+'ail'='AVAIL'
(Other definitions for avail that I've seen before include "(Of no) use or benefit" , "Serve a purpose" , "Make use, take advantage" , "Be of help or advantage" , "Help, benefit" .)