Source, average over time, becoming anxious to please (4-5)
I believe the answer is:
well-meant
'anxious to please' is the definition.
(as in well-meaning behaviour)
'source average over time' is the wordplay.
'source' becomes 'well' (well is a kind of source).
'average' becomes 'mean' (type of average).
'over' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'well'+'mean'+'t'='WELL-MEANT'
'becoming' is the link.
(Other definitions for well-meant that I've seen before include "Kind" , "Done with good intentions but poor result" .)