Trainer struggling to find ground (7)
I believe the answer is:
terrain
'ground' is the definition.
(terrain is land or ground)
'trainer struggling' is the wordplay.
'struggling' indicates an anagram.
'trainer' is an anagram of 'TERRAIN'.
'to find' acts as a link.
(Other definitions for terrain that I've seen before include "A stretch of land for trainer" , "Tract of land with particular character" , "Type of countryside" , "Stretch of land with respect to its character" , "Land (as base for action)" .)