In summer I captivate a lady... (5)
I believe the answer is:
erica
'lady' is the definition.
'in summer i captivate a' is the wordplay.
'in' indicates a hidden word.
'ERICA' can be found hidden inside 'summer i captivate a'.
(Other definitions for erica that I've seen before include "Woman" , "Shrubs" , "hardy shrub" , "Girl - heather" , "Heather's Latin name?" .)