Soldiers round a waterhole have good intentions (4,4)
I believe the answer is:
mean well
'have good intentions' is the definition.
(I've seen this in another clue)
'soldiers round a waterhole' is the wordplay.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'round' is an insertion indicator.
'waterhole' becomes 'well'.
'men' placed around 'a' is 'mean'.
'mean'+'well'='MEAN WELL'
(Other definitions for mean well that I've seen before include "Have good intentions but poor performance" , "Having intention to act properly" , "aim to please" , "with good intention" , "Want to he helpful" .)