Female struggling to walk, an erstwhile lover? (5)
I believe the answer is:
flame
'an erstwhile lover?' is the definition.
'female struggling to walk' is the wordplay.
'female' becomes 'f' (abbreviation).
'struggling to walk' becomes 'lame'.
'f'+'lame'='FLAME'
(Other definitions for flame that I've seen before include "Ignited gas" , "Blaze, burn brightly" , "Brilliant orange-red" , "Evidence of fire" , "lover?" .)