Lean back in playground row (7)
I believe the answer is:
recline
'lean back' is the definition.
('recline' can be a synonym of 'lean back')
'playground row' is the wordplay.
'playground' becomes 'rec' (I've seen this in other clues).
'row' becomes 'line' (I've seen this before).
'rec'+'line'='RECLINE'
'in' is the link.
(Other definitions for recline that I've seen before include "Assume horizontal or leaning position as for rest" , "Lean back, relax" , "Lie in a comfortable position" , "Lie back and take it easy" , "Lie back to rest" .)